HR: 16:00h
AN: S12F-01 INVITED     [PDF]
TI: Broad-band Seismology for Understanding Earthquake Physics and Developing a Modern Practice for Seismic Damage Mitigation
AU: * Kanamori, H
EM: hiroo@gps.caltech.edu
AF: California Institute of Technology, Seismological Laboratory, Pasadena, CA 91125 United States
AU: Heaton, T H
EM: heaton@gps.caltech.edu
AF: California Institute of Technology, Seismological Laboratory, Pasadena, CA 91125 United States
AB: In 1987, immediately after the 1987 Whittier Narrows earthquake, the Caltech broad-band regional seismic network project, TERRAscope, was launched under the direction of Don Anderson. At the time, UC Berkeley had also embarked on such a project. The objectives included: 1) Collect high-quality seismic data for developing theories of Earth's interior and exterior, 2) Develop a physics-based earthquake damage mitigation method, 3) Provide a test-bed for novel approaches in real-time seismology, 4) Provide an infrastructure for cultivating new directions in seismology. The data from TERRAscope, combined with those from other networks such as GDSN, IDA, IRIS, GeoScope networks were used to study various seismological problems, some of which had not been commonly investigated. We focus on three areas. The interaction between the solid earth and atmosphere had been the subject of considerable interest. The broadband networks detected interesting atmospheric waves from a few Hz ($N$ waves from space shuttles) to 0.001 Hz (Morning-glory waves. At the time it was not recognized as such). Also, it recorded monochromatic (period $\sim$ 230 sec) Rayleigh waves which were generated by the near source atmospheric oscillations excited by the 1991 Pinatubo eruption. These waves were not immediately recognized as such, because they had not been observed yet. This represents one of few cases in which significant energy transfer occurred from the atmosphere to the solid earth. These observations eventually led to the more ambitious ongoing projects for detecting ionospheric signature of acoustic and internal gravity waves in the atmosphere that couple into the solid earth. Gutenberg, together with Richter, published a series of papers on the energy of earthquakes in the 1940's to 1950's. The intent of these studies was to determine the most important quantity necessary for understanding the fundamental physics of earthquakes. Unfortunately, because of the overwhelming observational difficulties, the method remained largely empirical. One of the important objectives of the regional broad-band networks was to make a significant advance in this area. Early efforts turned out to be unsatisfactory, but the high-quality data obtained for the 1999 Hector Mine earthquake brought about significant progress. In the meantime, the methodology for determining earthquake rupture patterns made rapid progress, and details of rupture patterns were determined for many events. The patterns are all extremely complex reflecting the heterogeneities of fault-zone properties, and variations of the physical processes involved. The improvements in energy estimates (macroscopic parameter) and understanding of small scale, microscopic, structure and physics suggest a statistical mechanics approach to a better understanding of earthquake physics. An important objective of seismology is mitigation of earthquake damage. The complexity of earthquake physics, and the resulting unpredictability of exact rupture behavior make accurate prediction of earthquakes difficult. However, once the rupture occurs and seismic waves are generated, the behavior is controlled by elastic properties of the earth, and becomes more predictable. This concept, combined with the improved understanding of earthquake physics would lead to a novel approach to earthquake damage mitigation through real-time seismology, earthquake early warning, and predictive control theory for structures.
DE: 7200 SEISMOLOGY
DE: 7209 Earthquake dynamics and mechanics
DE: 7223 Seismic hazard assessment and prediction
DE: 7294 Instruments and techniques
DE: 7299 General or miscellaneous
SC: Seismology [S]
MN: 2003 Fall Meeting