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Title: Single-link cluster analysis of earthquake aftershocks: Decay laws and regional variations

Abstract

Using single-link cluster analysis, the authors investigate how various properties of aftershock sequences depend on their tectonic regime and focal depth. For International Seismological Centre earthquakes of m{sub b}{ge}4.8, they find that earthquakes deeper than 70 km have the fewest and smallest aftershock sequences. Even after accounting for differences in detectability and maximum magnitude, they find that ridge-transform earthquakes have smaller aftershock sequences that shallow subduction zone earthquakes. Among different subduction zones, they find that zones with high moment release rates possess larger aftershock sequences. Comparing ridge-transform zones, they find those with slower spreading rates possess larger aftershock sequences. By transposing origin times of several different aftershock sequences as if all had main shocks occurring at time zero, they are able to study the properties of aftershock sequences which individually have too few aftershocks to study by other means. Secondary events determined by single-link cluster analysis follow a modified Omori's (power law) decay for time separations of 0.1 day to 20 days from the parent event, with p values ranging from 0.539 {plus minus} 0.022 (intermediate- and deep-focus earthquakes) to 0.928 {plus minus} 0.024 (ridge-transform earthquakes). They find that earthquake foreshocks and multiplets also follow a modified Omori's law. Atmore » greater times from the main shock the decay is steeper than a power law decay, more like an exponential decay. Aftershocks in the Adak catalog (m{sub b}{ge}2.0) show a marked decrease in activity between 40 and 50 km depth. They speculate that the observed differences in number of aftershocks and p values may be caused by variations in fault heterogeneity or in fluid pressures.« less

Authors:
;  [1]
  1. Univ. of Texas, Austin (USA)
Publication Date:
OSTI Identifier:
5447027
Resource Type:
Journal Article
Journal Name:
Journal of Geophysical Research; (United States)
Additional Journal Information:
Journal Volume: 96:B4; Journal ID: ISSN 0148-0227
Country of Publication:
United States
Language:
English
Subject:
58 GEOSCIENCES; AFTERSHOCKS; DATA ANALYSIS; DEPTH; EARTHQUAKE MAGNITUDE; EARTHQUAKES; GEOLOGY; MATHEMATICAL MODELS; PRESSURE RELEASE; RESERVOIR PRESSURE; ROCK MECHANICS; STRESS RELAXATION; SUBDUCTION ZONES; TECTONICS; DIMENSIONS; MECHANICS; RELAXATION; SEISMIC EVENTS; 580000* - Geosciences

Citation Formats

Davis, S D, and Frohlich, C. Single-link cluster analysis of earthquake aftershocks: Decay laws and regional variations. United States: N. p., 1991. Web. doi:10.1029/90JB02634.
Davis, S D, & Frohlich, C. Single-link cluster analysis of earthquake aftershocks: Decay laws and regional variations. United States. doi:10.1029/90JB02634.
Davis, S D, and Frohlich, C. Wed . "Single-link cluster analysis of earthquake aftershocks: Decay laws and regional variations". United States. doi:10.1029/90JB02634.
@article{osti_5447027,
title = {Single-link cluster analysis of earthquake aftershocks: Decay laws and regional variations},
author = {Davis, S D and Frohlich, C},
abstractNote = {Using single-link cluster analysis, the authors investigate how various properties of aftershock sequences depend on their tectonic regime and focal depth. For International Seismological Centre earthquakes of m{sub b}{ge}4.8, they find that earthquakes deeper than 70 km have the fewest and smallest aftershock sequences. Even after accounting for differences in detectability and maximum magnitude, they find that ridge-transform earthquakes have smaller aftershock sequences that shallow subduction zone earthquakes. Among different subduction zones, they find that zones with high moment release rates possess larger aftershock sequences. Comparing ridge-transform zones, they find those with slower spreading rates possess larger aftershock sequences. By transposing origin times of several different aftershock sequences as if all had main shocks occurring at time zero, they are able to study the properties of aftershock sequences which individually have too few aftershocks to study by other means. Secondary events determined by single-link cluster analysis follow a modified Omori's (power law) decay for time separations of 0.1 day to 20 days from the parent event, with p values ranging from 0.539 {plus minus} 0.022 (intermediate- and deep-focus earthquakes) to 0.928 {plus minus} 0.024 (ridge-transform earthquakes). They find that earthquake foreshocks and multiplets also follow a modified Omori's law. At greater times from the main shock the decay is steeper than a power law decay, more like an exponential decay. Aftershocks in the Adak catalog (m{sub b}{ge}2.0) show a marked decrease in activity between 40 and 50 km depth. They speculate that the observed differences in number of aftershocks and p values may be caused by variations in fault heterogeneity or in fluid pressures.},
doi = {10.1029/90JB02634},
journal = {Journal of Geophysical Research; (United States)},
issn = {0148-0227},
number = ,
volume = 96:B4,
place = {United States},
year = {1991},
month = {4}
}