Station P494

Questions for Yehuda Bock

How did you become a scientist/engineer?

I went to Brooklyn Technical High School in New York City after doing well in science and mathematics in middle school. I went on to study math at NYU and engineering at the Israel Institute of Technology (Technion). That background and my experience in the artillery corps in the Israeli Defense Forces put me on a career path to do research in surveying and geodesy. I wanted a job that would be intellectually challenging, had societal impact and allowed me to work outdoors and travel to exotic places. At the time that I graduated with a degree in Geodetic Science from The Ohio State University (1982), it was clear that GPS was becoming an important tool for geophysical research. After working on developing GPS technology at MIT, I joined the faculty at Scripps Institution of Oceanography where I've been since 1989 working on geophysical applications of GPS.

What is your job like?

Being a researcher at the Institute of Geophysics and Planetary Physics at Scripps Institution of Oceanography is ideal for pursuing a rewarding science career. First, we are located on a cliff overlooking the beach in La Jolla and need to draw the shades to better concentrate. My work involves a wide range of activities from collecting GPS data throughout the West Coast and conducting field surveys in other countries to analyzing the data with modern computers, understanding the data, and applying that knowledge to real-world problems. For example, I spent about 1-2 months per year over a 10-year period collecting GPS data in Sumatra and throughout the Indonesian archipelago (including the island of Bali). These data proved crucial for understanding the 2006 Mw 9.1 earthquake and subsequent tsunami off the western coast of Sumatra, and later the 2011 Mw 9.0 earthquake and tsunami in Japan. Our technology may help reduce casualties during future extreme events, which are forecast for the Western U.S.

Combining GPS and Seismometers for Earthquake Early Response

When we drive in a car, we become familiar with the concepts of speed and acceleration. The dashboard displays the speed of the car, which is the magnitude of the car's velocity. When the car accelerates, that means the speed of the car is increasing; decelerating is when the car's speed is slowing down. Velocity and acceleration are also key pieces of information for Earth scientists. In particular, they want to know the velocity and acceleration of the ground during an earthquake. This teaches them both about the earthquake itself and how seismic waves propagate along the rupture. Measuring ground acceleration and velocity is also important for determining how to construct safe buildings. However, while traditional seismic instruments are pretty good at measuring acceleration and velocity, they are not good at measuring the position of the ground during an earthquake. For this information, scientists need to use GPS.

The GPS data from P494 are being used by the SOPAC research group in an earthquake early warning project. They are combining the acceleration data from a seismic instrument with the GPS data. This combined datastream will allow them to make warnings for the Western U.S. Their system takes advantage of the strengths of both systems - the seismometer is more precise, but unable to provide position; GPS is less precise, but optimized for positions. The combined data are used to determine:

• When (and where) an earthquake has occurred.
• How large the earthquake is.
• When the seismic waves generated by the earthquake will arrive at nearby large cities.

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