Authors

Deborah Kane, IGPP/SIO/UCSD, dlkane -@- ucsd.edu
Debi Kilb, IGPP/SIO/UCSD, dkilb -@- ucsd.edu
Arthur Berg, UCSD Mathematics Department, aberg -@- math.ucsd.edu
Vladik Martynov, IGPP/SIO/UCSD, vladik -@- epicenter.ucsd.edu

Project Description
Various studies have examined remote earthquake triggering in geothermal areas, but few studies have investigated triggering in non-geothermal areas. We search the ANZA (southern California) network catalog for evidence of remote triggering. Using three statistical tests (Binomial, Kolmogorov-Smirnov and Wilcoxon Rank-sum) we determine the significance of the rates and timing of earthquakes in southern California following large teleseismic events. To validate our statistical tests, we identify 20 local mainshocks (ML >= 3.1) with obvious aftershock sequences and 22 local mainshocks (Ml >= 3.0) that lack obvious aftershock sequences. Our statistical tests quantify the ability of these local mainshocks to trigger aftershocks. Assuming that the same triggering characteristic (i.e., a particular seismic wave amplitude, perhaps in a specific frequency band) is evident for both local and remote mainshocks, we apply the same tests to 60 remote mainshocks (Mb>=7.0) and assess the ability of these events to trigger seismicity in southern California. We find no obvious signature of remote triggering. We find minimal differences between the spectral amplitudes and maximum ground velocities of the local triggering and non-triggering earthquakes. Similar analysis of a select few of our remote earthquakes shows that the related ground motion regularly exceeds that of local earthquakes both at low frequencies and in maximum velocity. This evidence weakly suggests that triggering requires larger amplitudes at high frequencies and that a maximum ground velocity alone is not the primary factor in remote triggering. Our results are complex, suggesting that a triggering threshold, if it exists, may depend on several factors.