Seismicity Patterns, their Statistical Significance and Physical Meaning

204 Pure app!. geophys. , P. Reasenberg demonstrated that in Cascadia earthquakes are four times more likely to be foreshocks than in California. Many speakers emphasized the regional differences in all earthquake parameters, and it was generally understood that basic models of the earthquake occurrence must be modified for regional application. The idea that the focal mechanisms of foreshocks may differ from that of background activity was advocated by Y. Chen and identified by M. Ohtake as possibly the thus far most neglected property of foreshocks, in efforts to identify them. S. Matsumura proposed that focal mechanism patterns of small earthquakes may differ character istically near locked fault segments into which fault creep is advancing. Considerable discussion was devoted to the status of the seismic gap hypothesis because M. Wyss argued that the occurrence of the M 7. 9, 1986, Andreanof Islands earthquake was a confirmation of Reid's rebound theory of earthquakes and thus of the time predictable version of the gap hypothesis, whereas Y. Kagan believed he could negate this view by presenting a list of nine earthquake pairs with M> 7. 4, moment centroid separation of less than 100 km, and time difference less than about 60% of the time he estimated it would take plate motions to restore the slip of the first event.

Inhalt
Introduction: Seismicity Patterns, their Statistical Significance and Physical Meaning.- Rethinking Earthquake Prediction.- Is Earthquake Seismology a Hard, Quantitative Science?.- How Can One Test the Seismic Gap Hypothesis? The Case of Repeated Ruptures in the Aleutians.- Evolving Towards a Critical Point: A Review of Accelerating Seismic Moment/Energy Release Prior to Large and Great Earthquakes.- Seismic Cycles and the Evolution of Stress Correlation in Cellular Automaton Models of Finite Fault Networks.- Detailed Distribution of Accelerating Foreshocks before a M 5.1 Earthquake in Japan.- Foreshock Occurrence Rates before Large Earthquakes Worldwide.- Time Distribution of Immediate Foreshocks Obtained by a Stacking Method.- Pattern Characteristics of Foreshock Sequences.- Precursory Activation of Seismicity in Advance of the Kobe, 1995, M = 7.2 Earthquake.- The Variation of Stresses due to Aseismic Sliding and its Effect on Seismic Activity.- Precursory Seismic Quiescence before the 1994 Kurile Earthquake (Mw, = 8.3) Revealed by Three Independent Seismic Catalogs.- Seismicity Analysis through Point-process Modeling: A Review.- Representation and Analysis of the Earthquake Size Distribution: A Historical Review and Some New Approaches.- Universality of the Seismic Moment-frequency Relation.- Physical Basis for Statistical Patterns in Complex Earthquake Populations:Models, Predictions and Tests.- Use of Statistical Models to Analyze Periodic Seismicity Observed for Clusters in the Kanto Region, Central Japan.- Pore Creation due to Fault Slip in a Fluid-permeated Fault Zone and its Effect on Seismicity: Generation Mechanism of Earthquake Swarm.- Coupled Stress Release Model for Time-dependent Seismicity.- Recognition of a Locked State in Plate Subduction from Microearthquake Seismicity.- Seasonality of Great Earthquake Occurrence at the Northwestern Margin of the Philippine Sea Plate.- Eruptions of Pavlof Volcano, Alaska, and their Possible Modulation by Ocean Load and Tectonic Stresses: Re-Evaluation of the Hypothesis Based on New Data from 19841998.- Seismicity Patterns: Are they Always Related to Natural Causes?.