Saturday, December 5, 2009

U.S. Geological Survey and earthquakes in Afghanistan

An agreement between Afghanistan and the U.S. Agency for International Development and the USGS Policy Analysis and Science Assistance Branch (PASA) agreement was signed in September of 2004. This PASA initiated a USGS program in natural resources/hazards assessment for Afghanistan as part of the Afghanistan Reconstruction Program. The initial activities included coal, mineral and water resources assessments and earthquake hazard assessment. The U.S.Trade and Development Agency is also funding the USGS to conduct an oil and gas resources assessment of the country.

There are several hazards documents on the program webpage.  Included is a fact sheet on the earthquake hazard in Afghanistan.  It explains:
The nation of Afghanistan is located in a geologically active part of the world where the northward-moving Indian plate is colliding with southern part of the Eurasian plate at a rate of about 1.7 inches per year (43 mm/yr). This collision has created the world’s highest mountains and causes slips on major faults that generate large, often devastating earth- quakes. An example is the magnitude 7.6 earthquake on October 8, 2005, in Kashmir, Pakistan, which caused more than 80,000 fatalities and left an estimated 4 million people homeless.

Each year Afghanistan is struck by moderate to strong earthquakes, and every few years, a powerful earthquake causes significant damage or fatalities. As Afghanistan rebuilds following decades of war and strife, new construction and development need to be designed to accommodate the hazards posed by strong earthquakes. To assist in reconstruction efforts, the U.S. Geological Survey (USGS) has developed a preliminary seismic-hazard map of Afghanistan.

Click on the figure for a larger image.

As for the rest of the upcoming endeavors of the U.S. in Afghanistan, I tend to agree with Andrew Bacevich (see or listen to his interview on NPR, for example) that President Obama's decision to send more troops there is arbitrary and not well fitted to protecting us here at home, if indeed that is the goal.  The hope for quick success is ahistorical and based on faulty assumptions. But I guess those discussions should preoccupy other bloggers.

Friday, November 27, 2009

Turkey and earthquakes

The North Anatolian Fault in Turkey bears many resemblances to the San Andreas Fault. Both are similar in length, and have motion that is horizontal and right lateral, which means as you look across the fault, the side opposite moves to the right. (Believe me, this is true regardless of which side you stand on.) And, both pass through major population centers, Istanbul being at risk from the NAF. Just another place in the world where plates are jostling up against one another.

 Source: USGS

The graphic below is very cool, integrating lots of information about the geography and historical movement on this fault.  Edward Tufte would be pleased.

The Istanbul area seems overdue for some slip!

The World Bank (a group whose development policies and choice of directors I don't always agree with) has a nice high quality video (along with a number of others) on its YouTube channel, about the seismic retrofitting of buildings in this historic city.


What, you thought this was going to be about Thanksgiving?

Sunday, November 22, 2009

Seismograph mashups of the future?

Researchers at Cal Tech enlist public to help them measure earthquakes `block-by-block'
By Emma Gallegos, Staff Writer
Whittier Daily News
Posted: 11/22/2009 06:02:20 AM PST

PASADENA - Researchers at Caltech who study earthquakes want to enlist Southern Californians with cell phones or computers to help them measure strong jolts in the region.

A couple of years ago, the researchers noticed that accelerators - small devices that measure motion - were becoming common, and now they're practically a standard part of Macintosh laptops and touch-screen cell phones.

That's when it clicked that the accelerometers might help them with their research.

"Lightbulbs went on in people's heads - there's seismometers all over the place," said Tom Heaton, director of the Earthquake Engineering Research Laboratory at Caltech.

This summer the group of professors and students received a grant from the National Science Foundation to create a program that could use the data from thousands - if not millions - of accelerometers to give seismic experts a better picture of earthquakes and the faults that cause them.

Right now there are about 200 high-quality seismic stations throughout Southern California. There's one at the U.S. Geological Survey on the Caltech campus, but the next one is in Glendale.

That doesn't cut it for researchers, who would like to be able to get a block-by-block portrait of what happens when an earthquake strikes but can't afford to pay the $15,000 it costs to pay for and maintain these seismic stations.

"Instead of a small number of high-quality instruments, we'd rather (have) a
larger number of lesser-quality instruments, trading quality for quantity," said Robert Clayton, a Caltech professor in the seismological lab.

The accelerometers could not only help measure quakes block by block but also floor by floor, said civil engineering Professor Monica Kohler. She's interested in the way the data could help civil engineers understand how buildings move and sway when a quake hits.

There are a couple buildings that have seismometers installed, but they tend to be costly and intrusive, she said.

"It's become obvious that this is a very easy way to start putting sensors and getting building motions up potentially every floor of a high-rise building," Kohler said.

The accelerometers aren't as sensitive as pricey seismic stations, but industry demands have brought the costs of some down to $50 to $100.

The researchers already have a working model that transforms the same technology that deploys air bags in cars and makes the Nintendo Wii remote possible to measure strong quakes.

The test accelerometers aren't much larger than a quarter, and they can attach to laptops via a USB port. When you bang on the table where these laptops are sitting, a red spot appears on a Google map showing the "epicenter" of the quake centered on the Caltech campus.

Of course, once thousands or millions of these devices are hooked up to a ShakeOut map, researchers say that this everyday jostling and knocking on a table won't register as an earthquake.

It's the simultaneous motion of these accelerometers that will signal that an earthquake has occurred. The group is working to make sure that this information moves quickly - transmitted via a wireless signal and then out of the system where it will be safe.

"What we'd like to do is to be able to take the earliest motions and get the information out of the region as fast as possible," Clayton said.

He calls this the "Indiana Jones effect." After the first wave of a major earthquake, the infrastructure of the city and electrical systems will begin to fail in a wave. That information needs to be able to move ahead of the first wave of the earthquake, like Indiana Jones in the "Temple of Doom."

The group is planning to slowly release distribute the devices to the community, beginning in 2010, Clayton said.

Caltech community members will be the first to test the accelerometers. By spring, the group plans to release the accelerometers into the local school system, tapping into science teachers, who could use them as teaching tools. Next summer, the group will distribute them to other school systems in Los Angeles and to fire stations.

And if all goes well on this project in Southern California, Clayton said that the research could be applied to other earthquake-prone areas - especially developing countries that suffer from strong earthquakes but have a weak system for sensing them. It would be as simple as distributing the sensors to local Internet cafes.

"If you could put one of these in every Internet cafe, you'd have an instant seismic network," Clayton said.

Friday, November 20, 2009

Educational seismographs for discounted sale

DTA, formerly a U.S. Sales and Service Center for Guralp Systems, a world leader in the design and manufacture of low-noise broadband seismometers, is now in the process of closing down, and has a few Educational Seismographs ("PEPP" and "EDU" instruments) in its inventory for sale.  These instruments are fully operational.  The instruments are listed below, along with their condition and price.  Because DTA is closing down, warranties cannot be provided.  If you are interested in purchasing any of these instruments, conatct Bruce Pauly. Quotations will be prepared upon request.  Delivery would be immediate from the shelf.  First come first served.

PEPP Style:

PEPP-V     V7207     USED     $2000     (25% off)

PEPP-V     V7209     USED     $2000     (25% off)       

PEPP-T     T6285     USED     $5000     (25% off)

PEPP-T     T6284     USED     $3000     (55% off)     (no GPS receiver)

PEPP-V     V7219    NEW       $2160      (20% off)

EDU Style:

EDU-V       V7320     NEW      $2295     (15% off)

EDU-T       T6827      NEW      $5950     (15% off)

Tuesday, November 17, 2009

How to blog: plagiarize

Not Dillsburg this time, but Dilbert.

In my opinion, this approach is ok if you attribute your sources.  Think of me as an aggregator.

Oh, btw, I still have my 33 1/3 and 45 rpm vinyl records.

Saturday, November 14, 2009

Shaking Earth after one year

Happy first anniversary, some time fairly recently.

I noticed we are now listed as one of 175 blogs on the geoblogosphere.

We're still the only seismology blog written by professional geophysicists(s) on a more than weekly basis.

And, 20,000 hits in the last year, even if half of those are probably me.

Carry on.

Thursday, November 5, 2009

New edition of Earthquakes: Science and Society

Pearson Higher Education has published a new edition of David Brumbaugh's Earthquakes: Science and Society. The book has 272 pages, and the price is about $70 for the paperback edition.

According to Pearson, this text provides the basic scientific facts about earthquakes. It also explains how the study of earthquakes has progressed through time, offering details on the development of earthquake instruments, and covering practical aspects such as personal safety, building and living in areas prone to earthquakes, and earthquake geography.

The content is organized into three essentially independent sections:
  • Part I provides a primer on earthquake basics, with a survey of the historical development of human thought on earthquakes, including early scientific ideas and myths, from Poseidon to elastic rebound.
  • Part II considers how data gathered from earthquake instruments is used, and how the study of earthquakes has been applied to understand Earth.
  • Part III focuses on personal safety and earthquakes, considering what can be learned from past earthquakes and offering a what–not–to–do handbook.

Monday, November 2, 2009

Seismograph widget for your Macintosh

A while back, I wrote about the Macintosh program Seismac that would use the sudden motion sensor in your computer (you know, in case you knock your Mac off the table, to stop the hard drive) to display a 3-axis accelerogram. It is a great teaching aid.

My IT colleague Teb not only relieved me of some candy this weekend (with his kids), but he told me that this capability is now available for Macs as a "widget" (a little snippet of software).

You can download it from Apple. Free, only 141k. 
System requirements - Mac OS X 10.4 or later; Macbook, Powerbook or iBook

Thursday, October 29, 2009


Do you still use listservs? They used to be one of the coolest things online. Now we have Twitter (coughs, still unconvinced about Twitter).

It was 20 years ago that the 6.9 magnitude earthquake known as the "Loma Prieta" hit the San Francisco and Monterey Bay regions of California. The USGS has a brief description and collection of photos available at among many other sites. This was the World Series quake that occurred while the Giants were playing the A's.

Marty Hoag reports that after he heard about the quake, he wondered what we could do in the middle of the country. As an administrator of our LISTSERV(tm) service he decided to create an e-mail list. He expected it would be a temporary list and then disappear. But it is still running, as QUAKE-L.

You can review the entire archive and search the text of the postings at 

At first the focus was on the impact on computer networks (BITNET and the rather young Internet). For a few years there were discussions about earthquakes but early in the 1990 James Fisher started to provide the list with timely earthquake reports from the USGS. These are the main items on the list now. Currently there are 131 subscribers to the list. (I'm still one of them.)

Times are changing, though. If you haven't done so, just type the word "earthquake" into your Google search engine, and see what you come up with as the first hit. 

My son tells me that Twitters will be good in real-time emergency reaction and response. He is probably right, if the right Tweets can be heard over the technobabble.

To join the QUAKE-L list simply send e-mail to LISTSERV@LISTSERV.NODAK.EDU with SUBSCRIBE QUAKE-L in the BODY of the e-mail. 

Sunday, October 25, 2009

Second largest Dillsburg quake

The 2.8 magnitude quake occurred at 7:21 a.m. about two miles southeast of the York County town, according to the USGS Web site.
This was the biggest quake since the 2.9 event of 24 April, 2009.

Speaking of things rumbling in Pennsylvania ... well, see the image!

Friday, October 23, 2009

Earthquake early warning systems

There was an  interesting story on NPR a few days ago about the development of s seismic early warning system for California. Note that this is not earthquake forecasting or prediction, which might give days to years of warning about the possibility of a quake. Nor is it a tsunami warning system, which can give hours of warning that water waves may arrive across the ocean after an earthquake has already occurred.

Earthquake early warning systems use the travel time of seismic waves (around 5 miles per second!) to give a few seconds of warning before they arrive. So, in Japan, high-speed Shinkansen trains might be automatically slowed. Elevators could be forced to stop at the next floor.  Or, upon hearing sirens in the U.S. after the waves were sensed, you might have time to get below your desk. (Brings back memories from my youth of duck and cover drills).

As the article tells us, this effort is probably less effective than good earthquake planning and engineering, but a lot less costly then completely retrofitting San Francisco and Los Angeles.

Sunday, October 18, 2009

IRIS Seismographs in Schools Program

IRIS’s Seismographs in Schools Program serves teachers across the country and around the world using seismic instruments or real-time seismic data in K-16 classrooms. Additionally, the web site includes tools to share seismic data in real-time, classroom activities, and technical support documents for seismic instruments. The hope is to bridge the gap between science classrooms to create an international educational seismic network.

Join a growing movement of teachers using seismic data to engage students in science.

Friday, October 16, 2009

Report on the Dillsburg earthquake swarm

A new Open-File report presents information on the earthquake swarm in Dillsburg, York County, which began in October 2008. Data on microearthquakes were collected by an array of portable seismographs placed and operated by Lamont-Doherty Geological Observatory of Columbia University from October 24 to December 11, 2008. Results and interpretations based on this data are presented here. The Pennsylvania Geological Survey assisted in placement and monitoring of a later array from May to September, 2009. Data from that installation are still in processing and interpretation. A follow-up study, conducted by the Pennsylvania Geological Survey, Penn State University, Charles Scharnberger and Jeri Jones, will investigate the spatial and temporal distribution of seismic events during the summer of 2009, based upon the small array of seismographs that were in place during that period.

similar swarms in Pennsylvania, Maryland, Connecticut, South Carolina, Maine, Ontario, and elsewhere, have not led up to a big earthquake.  Rather, the activity has died away after several months.  Thus, it seems most likely that this is what will also happen with the Dillsburg swarm.
Full disclosure: I was the outside reviewer for this report.

Tuesday, October 13, 2009

Twenty years since the World Series Earthquake

My week on the Hayward Fault went without incident. Twenty years ago, California was not so lucky.  The World Series between the San Francisco Giants and the Oakland A's was interrupted by the Loma Prieta earthquake.

October 17, 2009 marks the 20th anniversary of the Loma Prieta Earthquake. At Stanford University, a panel of experts will reflect on what happened in 1989, the likely impact of future Bay Area earthquakes, progress in earthquake science and engineering, how the Bay Area can become more earthquake resilient, and earthquake preparedness.

Speaking of the World Series, go Phillies. And Yankees. What will I do if they face each other?

Thursday, October 8, 2009

Three magnitude 7's in one day

According to the list of earthquakes from the USGS, there were three magnitude 7 quakes on Oct. 7.

These all occurred near Vanuatu, so are probably not independent. But if we take the annual global magnitude statistics, there are typically 17 quakes per year with magnitudes above 7. What are the chances of getting three independent magnitude 7's on the same day?

The chance of getting one is 17/365 = 4.6%. I think (correct my joint probabilities, please) that the chances of three in one day would then be this probability cubed, or 1 chnce in 10,000,

If you are more energetic than I am, go back and check when was the last time this happened.

Or, would it make more sense to simply consider the probability of a magnitude 8 quake, which would release more energy than three magnitude 7's anyway?

Image from

Monday, October 5, 2009

My week on America's most dangerous fault?

I am visiting my sons and working for a week in Berkeley, California. So I've moved from the not so worrisome Lancaster Seismic Zone to

The Hayward Fault: Is It America’s Most Dangerous?

It passes right through the Cal football stadium:


The Cal team received quite a shock from USC on Saturday. But I was out at the best Americana music festival in the country, Hardly Strictly Bluegrass.

Tuesday, September 29, 2009

Magnitude 8.0 earthquake in Samoa, largest of 2009

Here is today's record on the Franklin and Marshall seismograph:

The U.S. Geological Survey lists this as the largest quake so far of 2009.

The tsunami warning has been cancelled.

Here is the basic info:
Location15.558°S, 172.073°W
Depth18 km (11.2 miles) set by location program

Sunday, September 27, 2009

Best of the Geoblogosphere

I don't link to many other blogs from here. I've kind of restricted myself to blogs that focus largely on earthquakes and that other endothermal process of volcanoes, and that have entries on a more or less weekly basis.

But of course, there are many others. Here is a list from last December of 100 best earth science blogs. I'd only been here for a couple of months at the time. Maybe I will crack into the next version of this list.


Thursday, September 24, 2009

Recovery funds for LCSN

From LDEO:

"That rumbling you feel is not necessarily a passing subway. New York City and the surrounding region gets a surprising number of small earthquakes, and a 2008 study from the region’s network of seismographs, run by Lamont-Doherty Earth Observatory, suggests that the risk of a damaging one is not negligible. This week, the federal government announced a major upgrade to that network.

"Lamont will receive $255,000 grant under the American Recovery and Reinvestment Act to beef up cables, power supplies and other hardware, and add monitoring staff for its 34 locations from Vermont down to Maryland. U.S. Representative Eliot Engel announced the grant, saying: “Because of the density of the population and the presence of such facilities as the Indian Point Nuclear Power Facility, it is essential that we monitor for [earthquakes].” Lamont is part of a national network, run in cooperation with the U.S. Geological Survey."

I'm wondering how they are going to find the $18 million blogging bonus I thought I was going to get out of that grant.

Wednesday, September 16, 2009

No rest for our very own Charles Scharnberger

Teaching Himself By Teaching Others
Intelligencer Journal-Lancaster New Era (PA)
Monday, August 24, 2009
Author: Lori Van Ingen

Retired Millersville University professor Charles Scharnberger believes learning throughout your adult life is important, and it's never too late to start.

Scharnberger said he believes that, in part, because of his father.

His father never graduated from high school, but when he retired at 65, he got a GED and then went on to get a college degree when he was in his 70s.

"That has particularly inspired me that it is never too late to learn," Scharnberger said. To that end, he teaches science classes for seniors.

Scharnberger finds that people who take lifelong-learner classes are interested and engaged in the subjects and bring their own life experiences to them.

"It makes it fun to teach these classes," he said.

He said there are several differences between lifelong learners and the average college-age student.

The senior lifelong learners are more relaxed than the college-age student, he said. They are not obsessed with grades; they are there because they really want to learn.

The participants in these lifelong learning classes are more or less the same age as the 66-year-old Scharnberger , so they share a common perception of things and come from the same point of reference, he said.

A native of St. Louis, Scharnberger earned his undergraduate degree in geology from Amherst College and his doctorate in geology from Washington University in St. Louis.

"My area really is geophysics - or physics applied to the earth. However, I taught a course in astrophysics," Scharnberger said.

Sunday, September 13, 2009

Lancaster seismic survey traverse

Here is a map of the seismic traverse through Lancaster County.

This crosses three physiographic provinces: the Triassic lowlands in the northern part of the county, the Piedmont lowlands in the central part of the county, and the Piedmont uplands in the southern part of the county.

Thursday, September 10, 2009

Will the seismic survey cause earthquakes?

From the Pennsylvania Geological Survey:

Does seismic surveying cause earthquakes or damage to property?

Seismic data collection does not cause earthquakes. Unless you are standing quite close, within a few feet of the equipment, you will not notice the vibrations from either the weight drop or the vibrating weight.

The risk of any damage comes from placing the weight on top of a shallowly buried pipe or cable. Part of the work prior to the start of the data collection is to identify the buried utilities in the data collection area. The location of these utilities within the public rights-of-way is generally well known, so the risk of damage is quite low. In the unlikely event any damage occurs from the work, the contractor is fully insured and will correct the problem quickly.
Download the entire circular here.

Sunday, September 6, 2009

Seismic survey in Lancaster County

I've been away for a bit: archaeomagnetic sampling and magnetic surveying at the Etruscan site of Poggio Colla in Italy; improving my field geophysics with folks at the Bayerisches Landesamt für Denkmalpflege in Munich; presenting a talk on magnetic properties of legacy sediments at the IAGA symposium in Sopron, Hungary; and along the way also enjoying the Venice Biennale and Budapest.

Anyway, what is shaking around here these days is seismic, but not an earthquake, It's a big truck. Lancaster County is getting "x-rayed" via vibroseis. Funding comes from Pennsylvania's carbon sequestration program.

Here is the full newspaper story, by PJ Reilly, from the Lancaster Intelligencer Journal, Jun 17, 2009:
A statewide project aimed at reducing Pennsylvania's carbon dioxide emissions could provide a first look at what's below the surface of Lancaster County.

"No one's ever drilled it deep," said Jay Parrish, director of the Bureau of Topographic and Geologic Survey for the state Department of Conservation and Natural Resources. "No one's ever done seismic work. All we know is what's at the surface.

"Everybody has seen the surface of Lancaster County for 250 years. Go down 3,000 feet and it's a complete mystery."

If his funding holds up, Parrish hopes to deploy a team to Lancaster County in August to literally pound the ground, north to south and from end to end, and take seismic readings to develop a picture of what lies deep beneath the surface.

"It's like a new world no one has ever looked at," he said. "We have no idea what's here."

DCNR is studying Pennsylvania's geology as part of the requirements of House Bill 2200, which was signed into law in October by Gov. Ed Rendell.

The bill orders DCNR to evaluate the state's potential for "geologic carbon sequestration."

According to the agency's Web site, that's a process in which carbon dioxide emissions are captured at coal-fired industrial plants before they are released into the atmosphere for injection and storage deep underground.

Pennsylvania ranks third among all 50 states for its total emissions of carbon dioxide, which is a greenhouse gas linked to global warming.

One percent of all the carbon dioxide emitted into the atmosphere in the world comes from Pennsylvania, Parrish said.

"As part of a broader portfolio of technologies, geologic sequestration appears to be capable of playing an important role in stabilizing carbon dioxide concentrations in the atmosphere," DCNR's Web site states.

Preliminary studies and general knowledge of Pennsylvania's geology suggest it is well suited for geologic carbon sequestration, which requires reservoirs a half-mile or more underground that are sealed by impermeable layers of rock, the Web site states.

Four primary reservoir areas DCNR expects to find are deep saline formations, depleted and producing oil and gas fields, coal beds that can't be mined and organic-rich shales.

Parrish, who was director of Lancaster County Geographic Information Systems department from 1997 to 2001, said his DCNR bureau has been assigned the task of studying the entire state to find such areas and others that might be suitable for storing carbon dioxide.

Scientists already know what lies beneath many areas of Pennsylvania, where coal mining and gas- and oil-well drilling have been going on for years.

But the extreme southeast corner of the state, including Lancaster County, is unexplored territory.

"Theoretically, there's no oil here, and that's why nobody has ever looked," Parrish said.

Discovering what lies beneath the county is important, according to Parrish, not only to see if the potential for carbon sequestration exists here, but also to simply have the subsurface data available.

"What does it mean to the average person?" he said. "It means there's a better understanding of the rocks under them, and that leads to every aspect of life, because you have radon flows, you have earthquakes, you have sinkholes.

"You just don't know what potential is there, and you also don't know, in the future, what may be useful information to have."

On Dec. 27, an earthquake measuring 3.4 on the Richter scale rattled Lancaster County. The epicenter was just west of Manheim Borough.

That's one of the areas Parrish wants to explore. He said scientists suspect there's a fault there, based on formations found in some local quarries.

"What we're looking at are little tiny thrusts at the top, so we have a good indication there's a fault there," he said. "But we don't know, maybe there's a huge faulted thrust underneath."

DCNR has budgeted about $3 million to collect seismic data from 41 of Pennsylvania's 67 counties, including Lancaster.

Parrish said the "project is in a constant state of flux" and "my priorities change from week to week," which could mean there won't be enough money to study Lancaster County.

For now, however, Parrish said the plan is for a seismic team to descend on the county in August.

He said it would take about three weeks to get readings along a north-south line through the heart of the county.

Since most of Pennsylvania's geologic formations run east to west, a north-south survey near the center of Lancaster County will give scientists a "pretty good idea" of what the whole county looks like beneath the surface, Parrish said.

To collect data, a large truck carrying a heavy weight would crawl along back roads at a rate of about 3 miles per day. Highways generate too much noise, which would interfere with the seismic readings, Parrish said.

Periodically along the route, the weight would be pounded on the ground and a series of small seismometers attached to a cable, which would be extended for three miles on both sides of the truck, would track the vibrations.

The data would be plugged into a computer "to give us a nice picture of the underground" up to three miles deep, Parrish said.

Ideally, Parrish would like to take readings on a perfectly straight line down the center of the county.

"Obviously, that's not possible with the roads we have around here," he said.

The line of readings likely will zig-zag along public roads.

Once he knows for certain there's enough money to study Lancaster County, Parrish plans to map out a work route and then contact officials in municipalities along that route to let them know what's happening.

"It's going to be a pretty big production that's going to attract a lot of attention," he said. "And we want people to know ahead of time what's going on."

Monday, July 27, 2009

Berkeley also blogs about moonquakes

See their story at Berkeley's Seismo Blog.

I couldn't have said it better myself.

Could those quakes be caused by a Man on the Moon?

Monday, July 20, 2009


I did think about an ode to the moon landing ... but there is just a little bit of that going on elsewhere.

But perhaps I should continue the thread of quakes on other heavenly bodies (no, I don't mean Brüno!).

According to a Stanford press release from last year:

"Scientists [my students inexplicably often write "scientist" in this kind of context, when they should use the plural - anyone else ever see that, or know why?] have shown for the first time that solar flares produce seismic waves, and gigantic seismic quakes, in the Sun's interior. Using data from the Michelson Doppler Imager onboard the European Space Agency/NASA Solar and Heliospheric Observatory (SOHO), Stanford and Glasgow scientists have tracked these seismic waves and found that "sun-quakes" closely resemble earthquakes on our planet.

"The researchers observed a flare-generated solar quake that contained about 40,000 times the energy released in the great earthquake that devastated San Francisco in 1906. The amount of energy released was enough to power the United States for 20 years at its current level of consumption, and was equivalent to an 11.3 magnitude quake on Earth."

Yikes, keep me away from that quake.

I'll be away in Europe on research for a few weeks. I'll be online from time to time, but maybe some of my colleagues would like to do some guest blogging.

Thursday, July 16, 2009

Apollo 11 - Moonquakes

It's 40 years today that Apollo 11 left Earth, and four days later humans first set foot on the Moon. I was a college lad, and I sat with friends around the tv to watch. What a stunning achievement - if only we could muster that same dedication, intelligence, creativity, and funding towards solving some of the critical issues that face us today.

From NASA: "Between 1969 and 1972, Apollo astronauts placed seismometers at their landing sites around the moon [as Buzz Aldrin is doing below]. The Apollo 12, 14, 15, and 16 instruments faithfully radioed data back to Earth until they were switched off in 1977."

"There are at least four different kinds of moonquakes: (1) deep moonquakes about 700 km below the surface, probably caused by tides; (2) vibrations from the impact of meteorites; (3) thermal quakes caused by the expansion of the frigid crust when first illuminated by the morning sun after two weeks of deep-freeze lunar night; and (4) shallow moonquakes only 20 or 30 kilometers below the surface.

"The first three were generally mild and harmless. Shallow moonquakes on the other hand" could yield magnitude 5.5 tremors.

Seismograms from three types of moonquakes recorded at the Apollo 16 station. LPX, LPY, and LPZ are the three long-period components and SPZ is the short-period vertical component. The first column shows a deep-focus moonquake; the center column, a shallow moonquake; the third column shows records of the impact of meteoroid on the lunar surface. [From ETH website; courtesy of NASA].

Wednesday, July 15, 2009

Largest quake of year in New Zealand, m=7.8

USGS 2009 earthquake statistics

The largest quake of 2009 to date, magnitude 7.8, happened today off the southern tip of New Zealand.
New Zealand Earthquake Report - Jul 15 2009 at 9:22 pm (NZST)
Magnitude 7.8
Latitude, Longitude - 45.75°S, 166.58°E
Focal Depth - 12 km
100 km north-west of Tuatapere
100 km south-west of Te Anau
160 km north-west of Invercargill
300 km west of Dunedin

New Zealand Seismograph Drum - Wether Hill Road (WHZ), Southland, New Zealand
This image represents one day's recording of the seismometer located near Wether Hill Road, in Southland, about 150 km from the epicenter.

The timestamp shown at the top right of the seismograph drum shown below is the time when this image was last refreshed. Each horizontal line (or trace) represents 30 minutes, each vertical line is spaced 1 minute apart; 24 hours of recording are displayed in total. The most recent signal is drawn at the bottom right hand corner of the drum. Then read the traces from right to left, bottom to top, to get from the most recent to the oldest signals. The trace will appear red if the signals are very large; this means they have been clipped to stop them overwriting too much of the surrounding image.

Maximum Modified Mercalli intensities of VII were indicated.

A tsunami warning was issued, but has been canceled.

Tuesday, July 14, 2009

How wood you do in an earthquake?

Today, Bastille Day, a six-story condominium building was shaken with same type of the motions of the 1994 Northridge earthquake, but one and a half times as intense--more powerful than any quake California has experienced in modern times.

The capstone experiment of NSF's multi-year NEESWood (it was harder than it should be to find out that stands for Network for Earthquake Engineering Simulation Wood) project, the effort will test new ways to construct buildings that can withstand severe forces of nature.

Working with the Japanese government's National Research Institute for Earth Science and Disaster Prevention (NIED), as part of a broader partnership with NSF, the NEESWood engineers tested their structure at the E-Defense facility, located north of Kobe, which houses the world's largest shake table.

On June 30th, the entire, sensor-laden structure was subjected to two tests, one simulating earthquake forces that occur, on average, once every 72 years and a second that would occur similarly once every 475 years. On July 6th, the same tests were run, but the steel-frame components were locked down, so only the six-story, wood-frame, residential structure would be affected.

Today the wood-frame structure became the subject of the largest shake table test the world has seen to date, at a level that equates to an event that occurs, on average, once every 2,500 years.
See photos and movies at NSF.

Sunday, July 12, 2009

Terremoto in Peru

My son was vacationing in Alaska and now in Peru, and then will live near my other son in the Bay Area. I wonder if they are seismophilic?

The magnitude 6.0 earthquake he might have felt in Peru today (ok, he is 1,000 km away in Lima) had me looking at the website of the Instituto Geofísico del Perú .

Not a bad site if you want to learn about earthquakes in Spanish.

Wednesday, July 8, 2009

L'Aquila and the G8 Summit

NPR, a favorite news source, had a good story this morning on the G8 Summit meeting in Italy and reconstruction following the magnitude 6.3 shock on 6 April. And thanks to audio stories, I know how to actually pronounce L'Aquila. (I guess you could get this from tv news, but I don't watch "news" on tv.)

There are still 65,000 homeless, and 25,000 people living in tents, and serious damage to many cultural treasures. (Photo below from NPR.)

You can read more or listen on NPR.

Perhaps this crisis is what has driven Italian Prime Minister Berlusconi to vice? Well, I'll give him credit for one thing - he hasn't (as far as I know) whined at a press conference about soulmates and higher callings.

Sunday, July 5, 2009

Philly quake - Murphy's seismograph law?

Our seismograph is down due to a bad hard drive.

So of course there is an earthquake in the area.


Small earthquake shakes NJ, Delaware, Pa.
The Associated Press

NEWPORT, Del. - The National Earthquake Center says a small earthquake felt Wednesday in the Wilmington, Del. area had its epicenter in southern New Jersey.

The center says the earthquake measured 2.8 on the Richter scale, up from an earlier estimate of 2.7. That's big enough to feel, but too small to cause much damage.

The epicenter was near Mannington Township, near the Delaware River.

Salem County deputy administrator Robin Weinstein says he felt shaking in his emergency management office soon after the quake began at 9:46 a.m. No injuries or damage were reported.

A spokesman for PSE&G Nuclear, which operates three nuclear power plants in Salem County, says the quake was too minor to register on the plant's monitoring devices."

Thursday, July 2, 2009

Senior seismologist olympics: earth shaking

I can only say this because, age-wise, I would qualify for the senior olympics!

"Charles K. Scharnberger, left, Helen Delano of the Bureau of Topographic and Geologic Survey and others jump to test a seismograph buried in the backyard of a Dillsburg area home on Friday. Over the years, residents of Moodus, Conn. have come to accept their earthquakes; in Dillsburg and Carroll Township, scientists and residents are still trying to figure out exactly what's happening." (Daily Record/Sunday News -- Jason Plotkin)

Sunday, June 28, 2009

Dillsburg, PA, re-visited

Here's a post I started about a month ago, but got deterred by North Korea:

What's happening under Carroll Township?

Updated: 05/30/2009 11:04:38 PM EDT Figure caption: (Daily Record/Sunday News -- Carrie Hamilton and Teresa Ann Boeckel)

Charles Scharnberger, retired earth sciences professor with Millersville University [and stalwart member of the LDCSN]:
Plate tectonics, or movements in the Earth's crust, plays a role in the big picture, he said. The North American Plate, which stretches from the middle of the Atlantic Ocean to California, is moving westward. The immediate picture is that rock is fracturing under the ground, and it's happening at a fairly shallow depth. The timing of the quakes and why they're happening in Dillsburg is what geologists don't understand. Many other places, besides Dillsburg, have strong contrasting bodies of rock -- igneous rock intruding into shale -- where stress is concentrated. It could be an ancient fault being reactivated, or it could be a new fault forming, he said.

Wayne Pennington, chairman of the Geological and Mining Engineering and Sciences Department at Michigan Technological University:
Earthquakes in general are caused by stress concentrations within the earth. The rocks break and slide. Faults are not big openings in the earth; they're like cracks in a sidewalk, he said. Rocks on one side won't line up with those on the other. Parts of the earth's crust are shifting, and stress can build up. It can be released in weaker spots. If a fault system is identified, the size of the fault will give experts a good idea of its maximum potential. It takes bigger faults to produce large earthquakes. The San Andreas fault, for example, is hundreds of miles long. If one exists in the Dillsburg area, it's probably not more than a few kilometers long, he said. A kilometer equals 0.62 miles. "It's, in a sense, the earth resettling," he said. Induced seismic activity, such as mines collapsing, is another possibility. It would result from the readjusting of rock near the stress void. The depths of the earthquakes would determine whether the mines are involved. If the mines are collapsing, the seismic activity that the area has been experiencing probably will not get any bigger.

George H. Myer, a professor of earth and environmental science at Temple University:
Earthquakes differ in California and the East Coast. In California, it's a side-to-side motion, known as a strike-slip fault. In Pennsylvania, they're known as normal or vertical faults. Normal faults push part of the rock downward, and vertical faults push the rock upward, he said. Geological maps show countless faults in the Dillsburg area, and it's possible that a reverse fault is at play. That's because of the booms residents are hearing. The primary waves refract off the surface and into the air, creating a vibrating noise that people can hear.

Thursday, June 18, 2009

San Andreas fault - amazing image

UAVSAR (Uninhabited Aerial Vehicle Synthetic Aperture Radar) image of the San Andreas fault in the San Francisco Bay area just west of San Mateo and Foster City. The fault runs diagonally from upper left to lower right. The body of water along the fault line is Crystal Springs Reservoir. Image credit: NASA/JPL

Sunday, June 14, 2009

Nuclear test statistics

I've done a fair number of blogs on small earthquakes in areas - Dillsburg, PA; Albany, NY - where the seismic threat is, after all, not very high.

Here are some historical statistics from 1945-2006 on nuclear testing (note the log scale on the y-axis):
Source: CTBTO (Preparatory Commission for the Comprehensive Nuclear-Test-Ban Treaty Organization)

This is a graph of tests, not warheads. Maybe we'll look at that in another post.

Thursday, June 11, 2009

Comprehensive Nuclear Test Ban Treaty

North Korea detonated a nuclear device on October 9, 2006. (a) A map of the region shows the location of the test (red star), nearby earthquakes (blue dots), and seismic monitoring stations (white triangles) at Mudanjiang in northeast China and Taejon, South Korea. (b) Seismograms recorded during the explosion (red wave) and a recent earthquake (blue wave) near that experiment show distinct P and S seismic waves for the earthquake, but not for the nuclear test (S&TR).
One more entry from Science & Technology Review, a publication of Lawrence Livermore Labs, which has an article on seismic verification of nuclear testing in its latest edition, although not late enough to mention the latest nuclear test of North Korea.

Monitoring the Comprehensive Nuclear Test Ban Treaty

"The U.S. ceased nuclear testing in 1992 in anticipation of the acceptance of the Comprehensive Nuclear Test Ban Treaty (CTBT). In 1996, President Bill Clinton and many other heads of state signed this multilateral treaty to prohibit all nuclear testing. Although most signatory countries ratified the treaty, the U.S. did not, and several countries required for the treaty to enter into force did not sign it. Expectations are high that the administration of President Barack Obama will reevaluate the CTBT’s role in nonproliferation policy.

"Although the CTBT is not in force, signatory countries and the U.S. are active participants in the International Monitoring System, which is overseen by the International Data Centre in Vienna, Austria, an organization established specifically to verify the CTBT. Every country supporting the system has a national data center. Livermore provides research and development support to the U.S. National Data Center at Patrick Air Force Base in Florida, which is responsible for U.S. nuclear test monitoring and international treaty verification.

"The International Monitoring System comprises a worldwide network of 337 sensitive monitoring stations and laboratories to detect nuclear explosions. Seismic stations anchored to bedrock record underground elastic waves, infrasound stations collect acoustograms from low-frequency sound waves aboveground, hydroacoustic stations in the oceans record underwater sound waves, and radionuclide stations measure airborne radioactive gases or particles. More than 230 of the recording systems now send data to the International Data Centre on a provisional basis. This unique network is designed to detect nuclear explosions anywhere on the planet—in the oceans, underground, or in the atmosphere.

"After the treaty enters into force, the signatory countries will have the role of identifying an event as a violation. The treaty also specifies several ways to resolve concerns about suspicious events, from consultation and clarification through a protocol that could lead to on-site inspections."

Saturday, June 6, 2009

Comment on explosions and fault plane solutions

Image from Wikipedia

I haven't yet figured out how to make the Comments in this blog visible without having to first click on the Comments blog. If you know how to do so, please clue me in.

Anyway, good question from my last entry, if you didn't see it: "Is there any way you'd consider sharing a higher-resolution version of that figure (say, big enough for a PowerPoint) with me? I'd like to use if for educational purposes (specifically in explaining the foundations of beach ball diagrams)."

I usually provide links to the text and figures I shamelessly borrow from other sources. So the best resolution you're gonna get is to go back to the source I used. In many cases, you can get a better resolution of the figures I post by clicking on the figure itself, and a better copy will open in a new window. Of course, I'd encourage you to retain the reference to the source if you re-use the figures in your own presentations.

One of the classic ways to distinguish seismic waves emanating from earthquake vs. seismic waves original from blasts, including underground nuclear tests, is that the energy from explosions is all directed radially outwards, while the initial pulse of energy from earthquakes is compressional in some quadrants, but dilatational in others. The global distribution of these compressional and dilatational first motions of seismic waves can be used to infer the orientation of the fault plane on which the earthquake occurred, and also whether the sense of motion is normal, reverse, or strike slip. This kind of analysis is known as a first motion study, fault plane solution, or focal mechanism solution. So earthquakes and explosions will yield quite distinct fault plane solutions.

I found a couple of decent resources if you want to learn more about earthquakes and fault plane solutions. There is a very nice online tutorial from Arild Andresen, University of Oslo. The Wikipedia page on focal mechanism look ok, and has two links at the end to a pdf file with more technical material for the geologist, and a cool page from the University of Bristol which lets you construct your own fault plane diagram.

But for your classroom demonstration, you have to see if you can find a beach ball that has four quadrants, not six. Faulty analogy, perhaps?

Thursday, June 4, 2009

More on seismic verification of nuclear tests

Science & Technology Review, a publication of Lawrence Livermore Labs, coincidentally has an article on seismic verification of nuclear testing in its latest edition, although not late enough to mention the latest nuclear test of North Korea. So the North Korea tests referred to are from 2006, not last month.

Part II of my cribbed comments focus on the Walter diagram for discriminating earthquakes from nuclear tests:

Various kinds of seismic events can be grouped on a source-type, or Hudson, plot based on their ground motion. A perfectly symmetric underground explosion would appear at the apex of the plot. By analyzing the seismic waves produced by the disturbance that rocked the Crandall Canyon Mine in Utah in August 2007, Laboratory seismologists determined that the event was an implosive tunnel collapse, not the sideways slippage of an earthquake.

"Distinguishing an earthquake from a nuclear event requires a close examination of the seismic waves. Such waves fall into two major categories: surface waves, which move along Earth’s surface, and body waves, which move through Earth and bounce off structures inside. Body waves may be primary (P) or secondary (S). Seismic P waves are compressional waves, similar to sound waves in the air. S waves are shear, or transverse, waves, similar to those that propagate along a rope when one end is shaken. Underground explosions radiate P waves in a relatively symmetric spherical shape. Earthquakes, which result from plates sliding along a buried fault, strongly excite the transverse motions of S waves, producing a distinct radiation pattern. Explosions thus show strong P waves and weak S waves. Earthquakes, in contrast, typically show weak P waves and strong S waves.

"But this information alone is not foolproof because the structure of Earth imparts an imprint on the signal. One way to quantify the difference between these seismic disturbances is to determine the ratio of P-wave to S-wave energy measured from the seismograms. Explosions should have higher P:S ratios than earthquakes.

"Recent Livermore work led by Walter sought to clarify the characteristics of the P:S ratios that distinguish nuclear weapons tests from other tectonic activity. By examining regional amplitude ratios of ground motion in a variety of frequencies, his team empirically demonstrated that such ratios indeed separate explosions from earthquakes. The researchers used closely located pairs of earthquakes and nuclear explosions recorded at monitoring stations at or near the Nevada Test Site; Novaya Zemlya and Semipalatinsk, former Soviet Union test sites; Lop Nor, China; India; Pakistan; and the North Korea test.

" 'At high frequencies, above 6 hertz, the P:S ratio method appears to work everywhere we looked,” says Walter. 'Explosions have larger P:S amplitude values.' For example, a test in India on May 11, 1998, compares well with the October 9, 2006, North Korea test.

"However, west of Pakistan, in the tectonically complex Middle East, seismogram analysis becomes more complicated. S waves attenuate, or lose energy, more rapidly in regions that are geologically complicated and seismically active. Seismograms from these areas tend to have larger P-wave amplitude relative to their S-wave amplitude. As a result, earthquake signals may look like those from an explosion. Because of these wave propagation effects, Walter’s team applied a tomographic technique to measure the highly variable attenuation of S waves in the Middle East.

"Tomography is a mathematical operation that uses variations in the waves passing through a material to construct an image of the material’s structure. For example, a medical tomography scan uses variations in the waves of x radiation transmitted through the body to produce an image that a radiologist can analyze. Tomography of Earth uses seismic waves to generate comparable images of Earth’s inner structure.

"The tomographic technique developed by Walter’s team models structural deformation based on the attenuation occurring as S waves propagate through different geologic media. Even with the precise algorithms in this tomographic attenuation method, however, some known earthquakes have P:S ratios that look like those of explosions. 'We expect that analysis of ground motion at higher frequencies will help us better understand and use this method,' says Walter. 'But we have only recently had the computational power we need to model high frequencies in 2D and 3D Earth models.' "

Monday, June 1, 2009

North Korea nuclear test - seismic verification

Science & Technology Review, a publication of Lawrence Livermore Labs, coincidentally has an article on seismic verification of nuclear testing in its latest edition, although not late enough to mention the latest nuclear test of North Korea.

I'm too lazy to paraphrase an article already well written. It starts out as follows:

AN earthquake, a nuclear test, and a mine collapse all cause seismic disturbances that are recorded at monitoring stations around the world. However, these three types of events produce very different ground motions at their source. Earthquakes are caused by sideways slippage on a fault plane, while underground nuclear explosions push outward in all directions. A mine collapse is a massive vertical roof fall.

Lawrence Livermore is at the forefront of research to more accurately distinguish nuclear explosions from the rest of Earth’s never-ending seismic activity, including earthquakes large and small, volcanoes, and waves crashing on shore. The Laboratory’s work was unexpectedly put to the test following the August 2007 collapse of the Crandall Canyon coal mine in Utah, which killed six miners. Ten days later, another collapse killed three rescue workers. Both events were recorded on the local network of seismic stations operated by the U.S. Geological Survey (USGS) as well as on the USArray stations, which are part of EarthScope, a program funded by the National Science Foundation. There was considerable contention about whether the initial magnitude-3.9 event was caused by an earthquake or a collapse.

At the time, Livermore seismologists were working with colleagues from the University of California at Berkeley on a waveform-matching technique to distinguish among nuclear explosions, earthquakes, and collapse events. This technique compares seismograms produced by computer modeling with recorded data at local to regional distances (from 0 to 1,500 kilometers) for periods of 5 to 50 seconds. Livermore’s analysis of the August 2007 seismograms pointed to a collapse rather than an earthquake. The important result for the Laboratory team was being able to identify the Crandall Canyon event from its seismic signature despite its small magnitude.

Livermore’s seismological research is part of the Department of Energy’s support for the U.S. National Data Center in the area of nuclear treaty verification. (See the box below.) The team’s experience with the Crandall Canyon Mine has given the Livermore seismologists even greater confidence that they can identify a relatively small nuclear test using the same technique.

More to come on this. Or go to the link, and read the whole article now.

Sunday, May 31, 2009

North Korea nuclear test seismogram - crustal phases

Back on January 17, I had an entry on crustal phases. We should do a short review to understand the nomenclature shown in the diagram in the last blog for the seismic phases seen on China seismograms after the Korea nuclear test.

You can find a listing of seismic phases here.

Note in particular the phases shown in the previous quake observed for the NK nuclear test:
  • Pg - at short distances, an upgoing P wave from a source in the upper crust; otherwise, a wave refracted from a mid-crustal discontinuity
  • Pn - a P wave refracted along the crust-mantle boundary
  • Sg - at short distances, an upgoing S wave from a source in the upper crust
  • Sn - an S wave refracted along the crust-mantle boundary
Rayleigh and L waves are surface waves.

Friday, May 29, 2009

North Korea nuclear test seismograms

Story and image from LDEO:

Seismologists who have intensively studied North Korea’s nuclear testing efforts say Monday’s blast was certainly a nuclear bomb, roughly five times larger than the country’s first test in 2006. The scientists, at Columbia University’s Lamont-Doherty Earth Observatory, say signals picked up by seismic stations including one in China close by, showed clear characteristics of a shallow underground nuclear explosion, with a force of probably several kilotons.

“The second test appears to have a significantly higher yield,” said seismologist Paul G. Richards, a longtime expert on seismic detection of nuclear tests. He and his colleague Won-Young Kim, also at Lamont, are coauthors of articles on the 2006 North Korean test in Nature Physics and Eos Transactions, and have a piece on current advances in nuclear-test detection in the March 2009 Scientific American.

Reports so far have given varying estimate of the explosion's size, and many suggest that only eventual leakage of radioactive particles into the air will confirm that the explosion was nuclear, not chemical. The assessment by Richards and Kim is in line with an anonymous Obama administration official who told The New York Times shortly afterward that it was a nuclear blast of “several kilotons.”

The seismic pattern produced by the latest blast was nearly identical to the Oct. 9, 2006, North Korean test, which later leaked radioactive particles. “The seismogram is almost a carbon copy of the previous image,” said Kim. Seismograms show two sudden, sharp jolts, followed by an angry buzzing of the earth. The dominant seismic waves produced were fast-traveling compressional, or P-waves, which alternately compress and dilate the ground outward from the source--the signature of an explosion. Earthquakes, by comparison, usually start out with weaker P-waves, and produce more shear waves, which shake the ground sideways in relation to their direction of travel. Kim said analysis of signals collected by different stations located the explosion in the same mountainous test area where the last test took place, some 40 kilometers northwest of the city of Kilju.

Richards said it was “implausible” that the blast, which produced shaking equivalent to an earthquake of magnitude 4.5 to 4.7, could have been made by surreptitiously planted conventional explosives. The explosion’s size cannot be exactly quantified because seismic measurements are influenced by the depth of the explosion, and the type of material in which it takes place. Geologic maps show that the surrounding area is made of hard granite and other rocks that transmit energy efficiently, but no one except the North Koreans knows the depth of the blast, nor whether it was in direct contact with bedrock. Kim put the blast in the range of 2.2 to 4 kilotons (a kiloton is equal to 1,000 tons of TNT). By comparison, the 2006 test was estimated to be less than a kiloton, and was considered by many to be only a partial success that did not completely detonate.

Other estimates of the current test have ranged widely. The Russian Defense Ministry said it might have yielded 15 or 20 kilotons—the size of the bombs that leveled Hiroshima and Nagasaki—while European scientists have estimated three to eight kilotons. However, some of these other estimates were made using data from stations far from the source, or which did not have readings from the 2006 event to use as a baseline. Richards and Kim took data only from a handful of stations that monitored the 2006 test, as well as earlier known chemical explosions and natural earthquakes in the same area that could be used for comparison. This included readings from the closest station from which data is available, in Mudanjiang, China, some 370 kilometers north of the test site. Much Chinese seismic data is unavailable to other countries, but Mudanjiang, operated with the U.S. Geological Survey and an international consortium of universities, transmits readings to researchers worldwide almost in real time. Kim and Richards also obtained information on signals from stations in South Korea, Australia, Alaska and Kyrgyzstan. Each showed amplitudes three to seven times higher than in 2006, leading to the conclusion that the new test had a yield roughly five times larger than the previous one.

By any account, the latest test blast was small compared with the bombs now stocked by major countries including the United States, which run upward of 50 megatons. But, said Richards, “Even the 2006 North Korean test would have been a disaster if it had gone off in a metropolitan area. This one was bigger.”

Wednesday, May 27, 2009

North Korea nuclear test, like m=4.7 earthquake

Underground nuclear tests generate seismic waves like earthquake. Properties of the seismic waves generated by these two mechanisms allow these types of events to be distinguished.

The seismogram of this event to the right is from the BBC.

According to the U.S. Geological Survey:

The shallow, magnitude 4.7 seismic event that occurred on 25 May 2009 at 00:54:43 UTC is linked to the claim of a nuclear test by North Korean officials. While the USGS cannot positively identify the seismic event as a nuclear test, it was shallow and located in the vicinity of the 9 October 2006 North Korean nuclear test (magnitude 4.3). Moreover, comparison of the seismograms of the 9 October 2006 and 25 May 2009 events at individual seismic stations shows similar features, suggesting that the two events are in close spatial proximity and are the same type of source, although the more recent event is larger.

Location41.306°N, 129.029°E
Depth0 km (~0 mile) set by location program
Distances70 km (45 miles) NNW of Kimchaek, North Korea
95 km (60 miles) SW of Chongjin, North Korea
180 km (115 miles) SSW of Yanji, Jilin, China
375 km (235 miles) NE of PYONGYANG, North Korea
Location Uncertaintyhorizontal +/- 3.8 km (2.4 miles); depth fixed by location program
ParametersNST= 75, Nph= 75, Dmin=371.4 km, Rmss=0.57 sec, Gp= 72°,
M-type=body wave magnitude (Mb), Version=A

More on nuclear tests and seismic waves to come.