Saturday, March 27, 2010

PBS Frontline - The Quake (Haiti)

The excellent PBS program Frontline is broadcasting a show this Tuesday on The Quake (the one in Haiti).

The trailer:

Online materials will also become available on March 30, and I hope I can stream the program online from Germany.

On Jan. 12, 2010, one of the most devastating earthquakes in recorded history leveled the Haitian capital, Port-au-Prince. Those responsible for handling the catastrophe, including the Haitian government and the United Nations, were among the victims. FRONTLINE correspondent Martin Smith (The Storm, Obama’s War) bears witness to the scale of the disaster and takes viewers on a searing and intimate journey into the camps, hospitals and broken neighborhoods of Port-au-Prince. Featuring never-before-seen footage of the moments after the earthquake and interviews with top officials from Port-au-Prince to Washington, The Quake, airing Tuesday, March 30, 2010, at 9 P.M. ET on PBS (check local listings), ultimately asks, how will the world respond?

Friday, March 26, 2010

The Risk Society

Yesterday I took a break from my sabbatical projects in Munich to attend an event at the Deutsches Museum (DM) sponsored by the Rachel Carson Center of the Ludwig-Maximilians University (LMU) and the DM.

It was very refreshing to listen for the day to academics from the social sciences and the humanities, who approach the "environment" with a different perspective, vocabulary, and mindset than we natural scientists do.

For the topic of this blog, perhaps my most interesting discovery yesterday was the concept of the risk society, part of the talk by Dr. Egner. At the "risk" or presenting the words of an unknown person, I will refer you to the entry on the risk society in Wikipedia - the idea of how modern societies deal with natural and manufactured risk, and how social relations are related to the nature of risk.  As I have previously blogged about, I think of seismic risk evaluation as a rather technical and objective exercise.  However, Dr. Egner's presentation discussed, from her perspective as a geographer, the social decisions that might go into a risk evaluation, and the differential impact of risk on various groups within a population.  I'm not sure I agreed with all of it, but the point of view was provocative. I think these ideas must be useful, for example, in contrasting the hazard situations related to the Chile and the Haiti earthquakes.

The Hasbro board game

Carson Workshop Program

Sherry Johnson, Florida International University, USA
Climate, Colonialism, Crisis, and Change in the Carribean in the Age of the Revolution, 1748-1804

Andrew Isenberg, Temple University, USA
The American Government Program in 1832 to vaccinate Indians against Smallpox

Martin Knoll, TU Darmstadt, Germany
Topographies of Nature - Nature of Topographies. Settlements, Territories, and Environment in early modern historicaltopographical Literature

Heike Egner, Universität Mainz, Germany
Space, Place and Knowledge: Natural Disasters and Cultures of Risk in Modern Societies

Gary Martin, Global Diversity Foundation, Marrakech, Morocco
Anthropogenic Forests, Agroecosystems and post-agrarian Landscapes: Local Knowledge Societies in a globalized World

Sunday, March 21, 2010

Earthquakes, urbanization, and fatalities

Roger Bilham is a fellow of CIRES,the Cooperative Institute for Research in Environmental Sciences, at the University of Colorado, Boulder. His research includes archival research into historical earthquakes, the statistics of urban earthquakes, and global seismic hazards. His web page on the Haiti earthquake includes a link to a news piece he wrote for Nature, where he argues that the destructiveness of the Haiti quake was due not only to its large (although not enormous) magnitude and energy release, but also the amplification of ground shaking by softer sediments, the proximity of Port-au-Prince to the epicenter, and especially to poor building construction practices in a large urban center.

He presents the rather fascinating diagram below, plotting fatalities against earthquake magnitudes:
Note that the vertical scale is logarithmic. There is a general correlation that larger magnitudes cause more deaths, but this is far from a linear plot. Notice that may of the most deadly quakes have been in fairly recent years, and don't highly correlate with magnitude. Why? Urbanization and poor construction. Better earthquake engineering is one of the reasons that the damage in Chile, although bad enough, was less than that in Haiti, although the Chilean quake was much larger.

Dr. Bilham comments:
With a Richter magnitude of M=7 the Haiti earthquake is classed as a major earthquake, however, no previous M=7 earthquake has resulted in this many fatalities (the Messina, Italy, earthquake of 1908 killed 82,000). At 230,000 the death toll is close to being the most lethal earthquake since 1900, and the second most lethal earthquake ever. The large death-toll was caused by the almost complete absence of earthquake resistance in most of the structures in Port-au-Prince and the surrounding towns and villages.

A recent article (2009) discussing the seismic future of cities may be downloaded here. It forecasts a rising death toll from earthquakes, especially in the developing nations, where earthquake resistance building codes are either absent or not enforced.

Saturday, March 20, 2010

Michio Kaku (tell us something new)

I sometimes add an entry related to the feeds that show up in the sidebar here, generated by a Google search that feeds into the page.

One of the entries there led me to the Big Think collection of blogs. This looks like an interesting site, one I will follow for a while to decide if I should add it to the few similar sites (Wired, Salon, Slate, NY Times, AlterNet) that I peruse on a regular basis.

I became aware of Michio Kaku, one of BT's contributing bloggers, some years ago, probably via a Nova special, I don't really remember. We certainly need scientifically oriented public intellectuals (think Carl Sagan, Stephen J. Gould) who can explain science to the public, and Kaku is one of those who, besides his stellar academic credentials, resides part of his time in that niche. Like Brian Greene, although Greene's presence online is a bit more sedate and academic-like.

(By the way, here is an interesting piece from NPR on quantum physics.)

Friday, March 19, 2010

Seismological Society of America Meeting

SSA 2010 Annual Meeting
21–23 April, Portland, Oregon

SSA’s 2010 Annual Meeting will provide a stimulating exchange of research on a wide range of topics with like-minded professionals from all over the world. Oral presentations, poster sessions, exhibits, field trips, business meetings and social gatherings all provide members the opportunity to meet and share with their peers.

Special Sessions:

Advances in Seismic Hazard Mapping

At the Interface Between Earthquake Sciences and Earthquake Engineering in the Pacific Northwest

Building Code Uses of Seismic Hazard Data

Characterizing the Next Cascadia Earthquake and Tsunami

Deterministic Simulated Ground Motion Records under ASCE 7-10 as a Bridge Between Geotechnical and Structural Engineering Industry

Engaging Students and Teachers in Seismology: In Memory of John Lahr

The Evolution of Slow Slip and Tremor in Time and Space

Ground Motion: Observations and Theory    

The January/February 2010 Earthquakes in Haiti, Offshore Northern California, and Chile: Origins, Impacts and Lessons Learned

On January 10 2010, a magnitude 6.5 earthquake ruptured a fault within the Gorda plate off the coast of Northern California, ending 15 years of relative seismic quiescence on California's North Coast and causing over $40 million in losses in Humboldt County. Three days later, a magnitude 7.0 earthquake occurred near Port-au-Prince, Haiti in an event that is likely to be listed as one of the great earthquake catastrophes of all time. We welcome papers addressing the mechanisms and tectonic settings of these earthquakes, the geotechnical factors, strong motion, remote sensing aspects, and direct observations of the earthquake zones including associated deformation, tsunami, landsliding and other evidence, as well as impacts and implications for regional seismic hazards. Addendum- This session will also include papers addressing these aspects of the Chile earthuake.

Magnitude Scaling and Regional Variation of Ground Motion

Monitoring for Nuclear Explosions

Near-Surface Deformation Associated with Active Faults

Numerical Prediction of Earthquake Ground Motion

Operational Earthquake Forecasting

Quantification and Treatment of Uncertainty and Correlations in Seismic Hazard and Risk Assessments

Recent Advances in Source Parameters and Earthquake Magnitude Estimations

Seismic Hazard Mitigation Policy Development and Implementation

Seismic Imaging: Recent Advancement and Future Directions

Seismic Networks, Analysis Tools, and Instrumentation 

Seismic Structure and Geodynamics of the High Lava Plains and Greater Pacific NorthwestSeismicity and Seismotectonics 

The Seismo-Acoustic Wavefield: Fusion of Seismic and Infrasound Data

Seismology of the Atmosphere, Oceans, and Cryosphere

State of Stress in Intraplate Regions

Statistics of Earthquakes

Subsurface Imaging for Urban Seismic Hazards at the Engineering Scale

Time Reversal in Geophysics

Volcanic Plumbing Systems: Results, Interpretations and Implications for Monitoring

Important Dates

Call for Special Sessions 1 October 2009
Travel Grant Application Deadline 30 November 2009
Abstract Submission Deadline 12 January 2010
Program w/ Abstracts Online 26 February 2010
Meeting Pre-registration Deadline 19 March 2010          TODAY
Hotel Reservation Cut-Off 29 March 2010
Online Registration Cut-Off 9 April 2010 

Field Trip Information:
Both field trips will take place on Saturday, 24 April 2010 (the day following the close of the regular meeting program).
Field Trip #1: Portland Geology by Tram, Train, and Foot
Field Trip #2: Geology and Hazards of Mount Hood, Oregon 

Thursday, March 18, 2010

Largest global earthquakes

There was an interesting pdf file from the USGS on the largest earthquakes (magnitude 8 and above) ever measured by seismographs. I have the link so you can download the file, but I can't even reconstruct where and how I found this. I did find a similar web page here.

Anyway, the three figures in the file are copied below.

The map shows the association of these large quakes with plate boundaries.  You can see the 2010 quake off the west coast of Chile, and the largest quake ever measured, nearby in Chile in 1960. The ones in the India-China region seem enigmatic, but they are presumably related to the collision of India and the rest of the Asian continent.

The figure below plots these events vs. time.  On the whole, this appears to be random.  There seems to have been a few more larger quakes in recent years, but there were even more in the late 50s-early 60s.   Hmmm, a Cold War effect?

The figure above shows the cumulative seismic moment, roughly a measure of total seismic energy released. Note how this pattern is dominated by the very largest quakes.

Tuesday, March 16, 2010

Chile aftershock report

The U.S. Geological Survey presents more interesting information on the Chile magnitude 8.8 quake here. The aftershock report notes

In the time period since the earthquake's origin at 2010-02-27 06:34 to 2010-03-15 15:00 UTC, the USGS NEIC has located 229 aftershocks of magnitude 5.0 or greater. Eighteen of these aftershocks have magnitudes of 6.0 or greater.

You've been hearing about many of these not insignificant aftershocks in the news.

Below is a current aftershock map, which can be found with updates here. Note the scale - these have been occurring along the plate boundary over a distance of about 1000 km, and over an area of about 50,000 square kilometers!

Monday, March 15, 2010

Chile poster - fault plane solution

With all the significant aftershocks after the 8.8 Chile aftershock, the accumulation of more data, and more analysis, the USGS poster has already changed.

But in my desire to present the different pieces of the earlier version of the poster, below is the fault plane solution (aka focal mechanism solution):

The fault plane solution, based on waves generated by the quake recorded at different seismic stations around the world, allows the inference of the type of faulting and the orientation of the fault plane.

The solution above is that of a nearly north-south striking fault. If the fault plane is dipping to the east, it is shallow; if it is dipping to the west, it is steep. Either would be consistent with the first motion analysis,but only the former makes more sense for the tectonic setting: the subduction of the Nazca Plate beneath the South Americn plate.

Arild Andresen of the University of Oslo has a very nice online tutorial on fault plane solutions.

Sunday, March 14, 2010

NPR - Are big quakes linked?

I have said previously that big quakes are not related, and that would still be my working hypothesis, but an NPR story (with text and audio) discusses this idea, and some related research. It also mentions, as I have, an aspect of random data (as earthquake occurrences may be): that events occurring at random times will not be evenly spaced in time, but occasionally either bunched up or further apart.

While on sabbatical in Munich, I now have the luxury of listening to NPR online, and if I listen to the archived shows (which I generally do because of the time difference), I can pick and choose the stories I want to hear. More or less this is good, but it does keep me from trying to better understand the German media, and allows me to fractionate the entire program that the NPR editors are presenting.  Still, better than my first sabbatical in Germany 20 years ago, at the dawn of email but really pre-www.  I had to struggle to understand German tv and newspapers, or spring for the pricey Herald Tribune once or twice a week, or go to the library to read it. Hey, come to think of it, that wasn't so bad, really.

Saturday, March 13, 2010

Chile poster - South American earthquake depths

Going back to my Shaking Earth entry of March 1, note the epicenters within the box using different colored symbols.

Compare this to the figure below from the Chile earthquake poster. This shows the depth of the quakes in the box of the earlier post, projected onto the central line.  The colors show the depths of the earthquake hypocenters  (or foci, plural of focus): red for depths of 0-69 km, green for 70-299 km, and blue for depths of 300-700 km. (The figure below doesn't show any blue dots.) But you can see the downward dipping slab of seismicity, also known as a Benioff zone, along the Nazca plate as it subducts beneath the South American plate.  There are also some shallow (red) quakes to the right,occurring in the overriding South American plate.  And, you will also note the volcanoes on the South American plate, represented by the yellow triangles.  These occur when the downgoing slab partially melts, and the magma rises to the surface.  This cross-section view (from the side) complements the earlier map or plan view (bird's-eye view) to give a three-dimensional representation of seismicity.

Wednesday, March 10, 2010

Chile earthquake moves South America 10 feet

Sunday I was in the Deutsches Museum in Munich, which has halls and halls full of scientific instruments and explanations, some more interesting than others.  I liked the historical instruments the most, such as the Magdeburg spheres.  There was one hall dedicated to geodesy, measuring the size and shape of the earth, and the surveying of its surface, from the use of chains and compasses to total stations to gps.

The Berkeley Seismo blog has a nice entry on the movement in South American due to the Chile earthquake. Concepción, near the epicenter, moved over 10 feet!  This is because earthquakes are caused by displacement on a fault.

I plan to discuss the westerly motion and its relation to the balloon diagram of the fault plane solution in a later post.

Figure from the Berkeley Seismo blog

Tuesday, March 9, 2010

Eastern Turkey earthquake leaves over 50 dead

The world keeps shaking.

Here is a news story from a Turkish source, the Hürriyet Daily News, about the earthquake in eastern Turkey that killed over 50 people.

And here is the report on this event from the Kandilli Observatory and Earthquake Research Institute, Bogazici University.

The recent quakes in the news - Haiti, Chile, Turkey - are NOT related, other than that they part of the global network of plate boundaries

Sunday, March 7, 2010

Chile earthquake intensities

Below is another clip from the USGS Chile earthquake poster showing the Modified Mercalli intensities from the recent 8.8 magnitude quake. Recall that magnitude is a seismograph-based estimate of the energy released by a quake and will be more or less the same for all seismic stations that record the waves. Intensities are evaluated according to human reactions and effects on buildings, are highest near the epicenter, and fall off with distance. I was surprised to see that Santiago has almost 5 million residents, so lots of people that are at risk.  The intensity in Santiago was VII ("Damage negligible in buildings of good design and construction; slight to moderate in well-built ordinary structures; considerable damage in poorly built or badly designed structures; some chimneys broken") on a scale of I-XII.

This map of the intensity data is a little easier to read:

No doubt about it, this was an intense event.

Saturday, March 6, 2010

Chile acceleration map

I spoke too soon. The USGS National Earthquake Information Center has posted a PGA map (peak ground accleration) for the Chile earthquake.

This is given as a contour map. Maximum values at the epicenter are about 30% of the acceleration due to gravity, which approaches the 50% shown on the seismic hazard projections of the last two blog entries.

Presumably, the blue dots represent data points from seismographs/accelerographs.

Friday, March 5, 2010

Slowing down on acceleration - Chile seismic hazard

Thank you to the anonymous commentator on my last post. Although it was not explicit in the USGS poster, it makes sense that the figure on acceleration would not represent actual data from the Chile quake.

As best I can tell, the source of the information is probably Figure 6 from an article by Shedlock and Tanner: Seismic Hazard Map of the Western Hemisphere, part of the Global Seismic Hazard Assessment Program.

This seismic hazard map of South America depicts the median peak ground acceleration (PGA) with a 10% probability of exceedance in 50 year. "PGA, a short-period ground motion parameter that is proportional to force, is the most commonly mapped ground motion parameter because current building codes that include seismic provisions specify the horizontal force a building should be able to withstand during an earthquake. This seismic hazard map of the Americas depicts the likely level of short-period ground motion from earthquakes in a fifty-year window. Short-period ground motions effect short-period structures (e.g. one-to-two story buildings)."

"There are three major elements comprising the method used to calculate the PGAs: "1) the characterization of seismic sources; 2) the characterization of attenuation of ground motion; and 3) the actual calculation of probabilities."

Thank you, Anonymous.

Fig. 6 from Shedlock and Tanner:

Thursday, March 4, 2010

Acceleration due to seismic waves - Chile poster

One of the primary hazards intrinsically associated with an earthquake is groundshaking.  This is a vector, with both horizontal ad vertical components.  The second derivative of the displacement is the acceleration.   Buildings are made to withstand vertical acceleration - after all, that is what gravity is.  However, by default, buildings are not engineered to withstand horizontal accelerations, although lateral bracing can be used, and should be within seismic zones.

The figure below, from our USGS poster on the Chile quake, plots ground motion accelerations from the Chile quake, and shows a couple of very interesting features. Note that the maximum acceleration caused by the Chilean quake is around 4.8 m/s2, which is half the acceleration of gravity (9.8 m/s2). That's pretty impressive. Also, note that the contours of equal acceleration run in a north-south direction, parallel to the plate boundary between the Nazca and South American plates.

Wednesday, March 3, 2010

Chile earthquake Facebook groups

 Social networking and aggregation of rss feeds can provide us with plenty (too much?) of information on breaking events.  I haven't really relied on these sites too much in the past, and have even been somewhat skeptical, but here are two Facebook grounps related to the Chile earthquake that you might want to look at:

Chile Earthquake


Chile Quake Recovery - NY Times .

I try to answer questions posed by readers. One asked about recovery from the even larger 1960 event. For now, see what the NY Times site above has to offer. I plan to talk more about damages and comparison of the Haiti and Chile quakes in an upcoming post.

Tuesday, March 2, 2010

Chile earthquake - tectonics in text

Does that make it the textonic? Text tonic?

We are working our way through the USGS poster on the Chile quake.

The text on the tectonic setting:
This earthquake occurred at the boundary between the Nazca and South American tectonic plates. The two plates are converging at a rate of 80 mm [3 inches] per year. The earthquake occurred as thrust-faulting on the interface between the two plates, with the Nazca plate moving down and landward below the South American plate. 
Coastal Chile has a history of very large earthquakes. Since 1973, there have been 13 events of magnitude 7.0 or greater. The February 27 shock originated about 230 km north of the source region of the magnitude 9.5 earthquake of May, 1960 the largest instrumentally recorded earthquake in the world. This magnitude 9.5 earthquake killed 1655 people in southern Chile and unleashed a tsunami that crossed the Pacific, killing 61 people in Hawaii, Japan, and the Philippines. Approximately 870 km to the north of the February 27 earthquake is the source region of the magnitude 8.5 earthquake of November, 1922. This great quake significantly impacted central Chile, killing several hundred people and causing severe property damage. The 1922 quake generated a 9-meter local tsunami that inundated the Chile coast near the town of Coquimbo; the tsunami also crossed the Pacific, washing away boats in Hilo harbor, Hawaii. The magnitude 8.8 earthquake of February 27, 2010 ruptured the portion of the South American subduction zone separating these two massive historical earthquakes. 
A large vigorous aftershock sequence can be expected from this earthquake. [As we will discuss, this has definitely been the case.]

Educational resources for the Chile earthquake

There is so much material out there on these devastating events ... hard to be selective, but in these times of supposed information overload, that's our challenge. I do want to work through more details of the USGS poster. And there are many fascinating news stories.

But today, especially for teachers looking for more educational resources on seismology, an excellent web site is that of IRIS, Incorporated Research Institutions for Seismology.

In particular, there is a page dedicated to resources on the Chile quake.

But there are slide shows, animations, fliers. Look around, and use what serves your purpose. That is what the educational mission of IRIS is about.

Monday, March 1, 2010

A closer look at the epicentral region, Chile quake

The figure below is another piece of the poster on the Chile quake available from the U.S. Geological Survey.

This figure includes quakes with magnitudes > 5.5, whereas the last figure only showed quakes with magnitudes > 7.

A couple of interesting patterns according to my eye:

1. Note that the epicenter of the main quake (yellow star) seems to fill a gap in the pattern of epicenter locations parallel to the Peru-Chile Trench, as if this part of the plate boundary was accumulating stress and needed some release. This, in fact, does happen (as I have previously reported in my Thanksgiving post for the North Anatolian Fault in Turkey), although I have not searched the scientific literature to see if that is actually the case here.

2. Note the aftershocks (orange circles) in the general vicinity of the main shock (star). They are not randomly distributed about the epicenter of the main quake, but are more linearly aligned, again parallel to the trench. So, the aftershocks also seem to be releasing some of the stress along the fault.

Stay tuned for more.