HR: 10:20h
AN: U12A-01 INVITED     [Abstracts]
TI: Earthquake Source Physics
AU: * Kanamori, H
EM: hiroo@gps.caltech.edu
AF: California Institute of Technology, Seismological Laboratory, Pasadena, CA 91125 United States
AB: Understanding the physics of earthquakes requires observational, theoretical, numerical, experimental, and field investigations. Seismological observations are generally on average macroscopic parameters (i.e., integrated quantities such as seismic moment, radiated energy, average stress drop etc), while most of the experimental and field observations are often on local microscopic parameters (i.e., friction, stress intensity factor, fracture energy, grain size of fault gouge, porosity etc). To construct a comprehensive earthquake source model, we need to link the macroscopic and microscopic source parameters. In this process spatial heterogeneities of fault properties and the vast difference (at least a factor of 1010) in time and length scales between earthquakes and laboratory observations need to be properly taken into account. The last decade has seen significant progress in linking them together with theory. Two main difficulties are: (1) no direct seismological method is available to determine the absolute level of crustal stresses and (2) the accuracy of macroscopic source parameters is not good enough to allow definitive interpretations, despite the increase in the quality and quantity of seismic data. In this tutorial presentation, I will summarize the recent progress in this field with an emphasis on recent seismological observations. Because of the two difficulties, the conceptual model still has a wide range of possibilities from very high shear stress on faults with low seismic efficiency to low shear stress with high seismic efficiency. However, regardless of these opposing views on the state of stress on faults, recent observations of the spatial-temporal energy release patterns of large earthquakes suggest that the earthquake process involves substantial chaotic elements and accurate predictions of its behavior are difficult. Nevertheless, the improved understanding of the physics of earthquake source suggests an effective damage mitigation measures through "earthquake early warning". This concept relies on a better understanding of the earthquake nucleation process and the recent advancement of numerical methods. Long term processes leading up to an earthquake have attracted seismologists' attention, especially those involving fluid motion in the crust. In particular, as one of the few cases in nature where the immediate cause of an earthquake is apparent, triggering provides a fundamental clue to initiation. I will briefly summarize the recent progress in this field.
DE: 7299 General or miscellaneous
DE: 7209 Earthquake dynamics and mechanics
DE: 7215 Earthquake parameters
SC: Union [U]
MN: 2004 AGU Fall Meeting