Decline of groundwater table in Beijing and recognition of seismic precursory information

This paper quantitatively analyzed groundwater table fluctuations caused by groundwater overdraft, and probed into the possibility of drawing earthquake precursory information from groundwater table variations on the background of groundwater overdraft. Main effect factors of groundwater regime in Beijing region include groundwater extraction and rainfall. The decline of groundwater table was directly related to regional groundwater overdraft. Using the method of correlation analysis, the paper analyzed the relation between groundwater overdraft and groundwater level variations, with the aim of evaluating the effect of groundwater overdraft on water levels in observation wells and providing scientific basis for identifying seismic precursory information. The results indicate that the variations of groundwater level in slightly-affected zones of groundwater overdraft can contain some seismic precursory information, and it is possible to extract seismic precursory anomalies if proper mathematical methods are adopted to remove the trend component and annual period changes.

Earthquake hazard potential in the Eastern Anatolian Region of Turkey： seismotectonic b and Dc-values and precursory quiescence Z-value

The Eastern Anatolian Region of Turkey is one of the most seismically and tectonically active regions due to the frequent occurrence of earthquakes. Thus, the main goal of this study is to analyze the regional and temporal characteristics of seismicity in the Eastern Anatolia in terms of the seismotectonic b-value, fractal dimension Dcvalue, precursory seismic quiescence Z-value, and their interrelationships. This study also seeks to obtain a reliable empirical relation between b and De-values and to evaluate the temporal changes of these parameters as they relate to the earthquake potential of the region. A more up-to-date relation of De = 2.55 -0.39＊b is found with a very strong negative correlation coefficient （r=- 0.95） by using the orthogonal regression method. The b-values less than 1.0 and the De-values greater than 2.2 are observed in the Northeast Anatolian Fault Zone, Askale, Erzurum, Igdlr and Caldlran Faults, Dogubeyazlt Fault Zone, around the Genc Fault, the western part of the Bitlis-Zagros Thrust Zone, Pulumir and Karakogan Faults, and the SancakUzunpmar Fault Zone. In addition, the regions having small b-values and large Z-values are calculated around the Geng, Piulumur and Karakogan Faults as well as the Saneak-Uzunpmar Fault Zone. Remarkably, the combinations of these seismotectonic parameters could reveal the earthquake hazard potential in the Eastern Anatolian Region of Turkey, thus creating an increased interest in these anomaly regions.