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TitleDelineating complex spatiotemporal distribution of earthquake aftershocks: an improved source-scanning algorithm
AuthorLiao, Y -C; Kao, H; Rosengerger, A; Hsu, S -K; Huang, B -S
SourceGeophysical Journal International vol. 189, 2012 p. 1753-1770, (Open Access)
Alt SeriesEarth Sciences Sector, Contribution Series 20110419
PublisherRoyal Astrological Society
Mediapaper; on-line; digital
File formatpdf
Subjectsgeophysics; earthquakes; earthquake studies; earthquake mechanisms; aftershocks; seismology; seismological network; seismographs
Illustrationsgraphs; plots
ProgramTargeted Hazard Assessments in Western Canada, Public Safety Geoscience
Released2012 04 16
AbstractConventional earthquake location methods depend critically on the correct identification of seismic phases and their arrival times from seismograms. Accurate phase picking is particularly difficult for aftershocks that occur closely in time and space, mostly because of the ambiguity of correlating the same phase at different stations. In this study, we introduce an improved Source-Scanning Algorithm (ISSA) for the purpose of delineating the complex distribution of aftershocks without time-consuming and labour-intensive phase-picking procedures. The improvements include the application of a ground motion analyser to separate P and S waves, the automatic adjustment of time windows for 'brightness' calculation based on the scanning resolution and a modified brightness function to combine constraints from multiple phases. Synthetic experiments simulating a challenging scenario are conducted to demonstrate the robustness of the ISSA. The method is applied to a field data set selected from the ocean-bottom-seismograph records of an offshore aftershock sequence southwest of Taiwan. Although visual inspection of the seismograms is ambiguous, our ISSA analysis clearly delineates two events that can best explain the observed waveform pattern.