Seminar hosted by the Earthquake Hazards Team, U. S. Geological Survey in Menlo Park
10:30 am, Feb. 04, 2009, videocast at:
http://earthquake.usgs.gov/regional/nca/seminars/
EHZ Seminar Video
http://earthquake.usgs.gov/regional/nca/seminars/video/index.php?id=2009-02-04
Our collective fear of earthquakes is to a large extent based on our inability to understand the various fleeting, often subtle signals, which the Earth sends out prior to major seismic events. However, earthquakes mark only the end stage of a long drawn-out process, during which stress builds up deep below. It is inconceivable that the preparation of large earthquakes would not be accompanied by precursory signals. Indeed, pre-earthquake signals have been widely reported. They range from ionospheric perturbations, "Thermal anomalies" seen in satellite images, low frequency EM emissions, to even unusual animal behavior. They are enigmatic and diverse. Until now nobody could say how these different signals are generated and how they fit together.
Key to deciphering pre-earthquake signals is the discovery of electronic charge carriers in rocks. Previously unknown, these charge carriers exist in all rocks, albeit in a dormant form. When rocks are stressed, they "wake up". They flow out like a current flows out of a battery. They travel fast and far, meters in the lab, kilometers in the field. Under specific conditions they can form powerful electric currents that lead to strong electromagnetic signals. When they reach the Earth surface, they ionize the air and cause a range of secondary reactions. With the recent progress on the scientific front we can now say with some degree of confidence that we begin to understand pre-earthquake signals and what they can tell us. Now we can start thinking how to use them effectively as earthquake early warning signs - to save lives and to mitigate material damages.
Friedemann T. Freund is with the NASA Ames Research Center, Earth Science Division, Moffett Field, CA 94035-1000. He is Adjunct Professor, Department of Physics, San Jose State University, San Jose, and Principal Investigator at the Carl Sagan Center, SETI Institute, Mountain View, CA.
Dr. Freund came to NASA Ames after a 20-year career as professor in Germany at the universities of Gottingen and Cologne. His field of interest started with defects in crystals. This led to studies of questions related to the origin of Life and, as a spin-off, to the physics of pre-earthquake signals.
Towards a Unified Theory for Pre-Earthquake Signals (Quakefinder)
Earthquake Lights Lecture Online (About.com)
Earthquake warning theory draws criticism (abc 7)
NASA Ames Researchers Work On Quake Warning System (CBS 5)
FAQ - Earthquake Effects & Experiences (USGS)
Anticipating Earthquakes (NASA)
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