seismology – Marin Science Seminar

by Zack Griggy, San Marin HS

The earthquake is an awe-inspiring disaster that can occur anywhere at anytime where two tectonic plates contact. Tectonic plates make up most of the Earth’s crust and move freely, so they can rub up against, move away from, or compress against other tectonic plates, which results in huge amounts of energy. The place where said actions occur are called faults. Earthquakes are the result of rocks along the fault breaking as the faults move. This releases all the pent-up energy from the tectonic plate movement, and results in a tremor. There have been countless earthquakes recorded, but recently, there have been many events in particular that have attracted a large amount of attention in the seismological community, among which include the San Ramon Swarm and last April’s Nepal Quake.

Destruction from April’s Nepal Earthquake

Since October 15, the town of San Ramon in Contra Costa County, California has been rattled by more than 200 small earthquakes. Thirty of which occurred over two days. The tremors have been small, the largest to date barely reaching 3.2 on the Richter Scale. According to the US Geological Survey, there have been numerous instances of earthquake “swarms,” where numerous earthquakes occur in a close vicinity and in a short period of time. However, the past swarms have occurred over a long period of time, which raised the question of how long this swarm will last. The longest swarm was in the nearby town of Alamo that lasted 42 days with over 350 earthquakes. Residents are concerned about the earthquake swarm but seismologists say that the swarm may be beneficial, because the fault is releasing pent up energy and abating the risk of a large magnitude tremor for years to come.
However, earthquakes are very capable of wreaking havoc into both the developed and undeveloped world. The recent Nepal Quake of last April is an example of the destructive power earthquakes possess. This quake, centered about 85 miles from Nepal’s capital of Kathmandu, was responsible for the death of over 8000 people and the destruction of over half a

A diagram that shows the risk for earthquakes worldwide

million homes. Millions are still in need of humanitarian aid because of this quake and its aftershocks. The quake reached 7.8 on the Richter Scale, which made this tremor more than 800 thousand times stronger than the strongest tremor in the San Ramon Earthquake Swarm. What really raises concerns however, is the realization that a quake like this could happen almost anywhere. According to TIME, the three cities most at risk for a large magnitude earthquake are Tehran, Istanbul, and Los Angeles. These are densely populated cities, and the fallouts of a large earthquake there could be devastating.

Sources:
1. http://www.ktvu.com/news/east-bay-news/32982571-story
2. http://www.sfgate.com/bayarea/article/Small-earthquake-strikes-in-area-of-recent-swarms-6590014.php#photo-8857844
3. http://www.ga.gov.au/scientific-topics/hazards/earthquake/basics/causes
4. http://time.com/3882272/nepal-earthquake-death-toll-2/
5. http://time.com/3838716/earthquake-risk-nepal/

To learn more about earthquakes and the science behind them, attend Dr. Diego Melgar’s presentation on Wednesday, November 15, 2015 from 7:30 – 8:30 at Terra Linda High School, Room 207, 320 Nova Albion Way.

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By Talya Klinger, MSS Intern

How can we meet the computational challenge of modeling and monitoring earthquakes in real time, and how can we anticipate and prepare for natural disasters? Diego Melgar, Ph.D. of the UC Berkeley Seismological Laboratory, is investigating these questions and more. As an assistant researcher, he develops earthquake models and tsunami warning systems using high-rate GPS data, paving the way for better earthquake preparation.

1. How did you first get interested in seismology?

I grew up in Mexico City, where earthquakes, volcanoes, hurricanes and other natural hazards are a fact of life. I’ve also always liked math and physics, and so, when it was time to go to college and select a program, I looked around and I found a geophysics degree at the National University that studied the Earth and its physics with lots of math. It seemed like a great idea to me!

2. What are some of the most challenging aspects of modeling natural disasters in real-time?

That they are complex and that measurements are sparse. Many things are going on during an earthquake or any other natural hazard, they’re really complicated! Saying something about them very quickly with sparse observations and being right about it is a real challenge.

3. How do you go about making tsunami propagation models more efficient?

We run them in parallel on bigger computers. We can now make very detailed models of the tsunami in less than one minute.

4. How does the technique of real-time monitoring impact geological research and natural disaster preparation?

Basic research allows us to find out what are the laws of physics and chemistry that make earthquakes and other hazards do what they do, it lets us find about what makes the Earth tick. In turn, the more we know about the physics and chemistry of the Earth the more intelligent we can make our warning systems, we can provide more relevant and precise information in shorter periods of time.

5. Tell us about your work in analyzing the magnitude 7.8 earthquake in Nepal: what did you discover about its source?

Nepal was a very interesting event because in spite of the fact that there were thousands of casualties and widespread destruction, it really could have been a lot worse. Given the state of development of the country we could have easily seen 150,000 casualties like we did in Haiti in 2010, but we did not. After some research we learned that part of the reason for this is that the earthquake rupture was very smooth and that smoothness lead to less shaking than we would have expected.

6. Finally, what advice do you have for students who are interested in seismology, geophysics, or signal processing?

Learn physics, learn math, and learn computers. Earth sciences are an incredibly rich field where these tools are really important. But also go outside, go hiking, look at rocks, notice how each one is different and wonder where they came from. The Earth is a beautiful laboratory and we should enjoy it with our minds but we should also go out and experience it.

To find out more, watch Dr. Melgar’s Marin Science Seminar presentation on November 18th, 7:30-8:30 pm at Terra Linda High School, Room 207.

Category: seismology

A Tale of Two Tremors: The Nepal Quake and the San Ramon Swarm

Modeling Tsunamis and Monitoring Earthquakes: an Interview with Geophysicist and MSS Speaker Diego Melgar