[1] This paper investigates the shallow seismicity occurring in the Taiwan region during the 20th century using a stochastic declustering method that has been developed on the basis of the theory of the epidemic-type aftershock sequence model. It provides a probability based tool to objectively separate the space-time occurrences of earthquakes into a background and a clustering component. On the basis of the background and clustering seismicity rates, we discuss the correlation between the distribution of the cluster ratio and the regional seismotectonic structures. Specifically, we find that the areas of the highest clustering ratio correspond to the major strike-slip fault traces in and around Taiwan. Additionally, in the Taiwan inland region, during the period 1960-1990, the outputs for the stochastically declustered catalogue show a clear quiescence in background seismicity preceding the recovery of activation and the occurrences of the 1999 Chi-Chi earthquake of M L 7.3, while the other active regions show stationary background activity. This could be interpreted as an effect of the aseismic slip in the Chi-Chi rupture fault, whereby the inland region around the Chi-Chi source becomes a stress shadow. (2005), A study on the background and clustering seismicity in the Taiwan region by using point process models,
[1] Tsunami ionospheric disturbances (TIDs) of the 26 December 2004 M w 9.3 Sumatra earthquake are detected by the total electron content (TEC) of ground-based receivers of the global positioning system (GPS) in the Indian Ocean area. It is found that the tsunami waves triggered atmospheric disturbances near the sea surface, which then traveled upward with an average velocity of about 730 m/s (2700 km/hr) into the ionosphere and significantly disturbed the electron density within it. Results further show that the TIDs, which have maximum height of about 8.6-17.2 km, periods of 10-20 min, and horizontal wavelengths of 120-240 km, travel away from the epicenter with an average horizontal speed of about 700 km/hr (190 m/s) in the ionosphere.
To verify the pre-earthquake ionospheric anomaly (PEIA), statistical analyses are implemented on the relationship between the total electron content (TEC) of global ionosphere map (GIM) and 62 M ≥ 6.0 earthquakes in China during 1998 -2015. A median-based method together with z test is employed to determine the criteria and/or characteristics of TEC anomalies related to earthquakes. , 18 -20 days before 7 M ≥ 7.0 earthquakes. The receiver operating characteristic (ROC) curve is used to compare the TEC anomaly-based method with some competitive alternatives for predicting the earthquakes under study. We found, based on possible TEC anomalies, that the observed PEIAs are significantly earthquake-related. Moreover, the results of regression analyses show that the PEIA strength is associated with the magnitude of earthquakes.
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