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摘要
Periodic earthquake occurrences may reflect links with semidiurnal to multiyear tides, seasonal hydrological loads, and similar to 14 month pole tide forcing. The Schuster spectrum is a recent extension of Schuster's traditional test for periodicity analysis in seismology. We present an alternative approach: the multifrequential periodogramanalysis (MFPA), performed on time series of monthly earthquake numbers. We explore if seismicity in two central California regions, the Central San Andreas Fault near Parkfield (CSAF-PKD) and the Sierra Nevada-Eastern California Shear Zone (SN-ECSZ), exhibits periodic behavior at periods of 2 months to several years. Original and declustered catalogs spanning up to 26 years were analyzed with both methods. For CSAF-PKD, the MFPA resolves similar to 1 year periodicities, with additional statistically significant periods of similar to 6 and similar to 4 months; for SN-ECSZ, it finds a strong similar to 14 month periodic component. Unlike the Schuster spectrum, the MFPA has an exact modified statistic at non-Fourier frequencies. Informed by the MFPA period estimates, trigonometric models with periods of 12, 6, and 4 months (Model 1) and 14.24 and 12 months (Model 2) were fitted to time series of earthquake numbers. For CSAF-PKD, Model 1 shows a peak annual earthquake occurrence during August-November and a secondary peak in April. Similar peaks, or troughs, are found in annual and semiannual components of pole tide and tide-induced stressmodel time series and fault normal-stress reduction from seasonal hydrological unloading. For SN-ECSZ, the dominant similar to 14 month periodicity prevents regular annual peaking, and Model 2 provides a better fit (Delta(R) over bar (2)(adjusted): 2.4%). This new MFPA application resolves several periodicities in earthquake catalogs that reveal external periodic forcing.
- 出版日期2015-12
- 单位McGill; 防灾科技学院
