第66回統計地震学セミナー / The 66th Statistical Seismology Seminar

Eastern Tibet is one of the most tectonically active areas in Chinese Mainland. Songpan-Ganzi Block, Longmenshan Orogenic Belt, and Sichuan Basin are located in this area from west to east. The uplifting mechanisms of eastern Tibet are hot debated in recent years. In addition, a series of great earthquakes in eastern Tibet (2008 Wenchuan Mw7.9, 2013 Lushan Mw6.6, and the most recent 2017 Jiuzhaigou Mw6.5) show the urgent need for accurate seismicity detection, as we are still not clear how aftershocks evolve because of the poor station coverage and overlapping of aftershocks.

Here, I would like to present our studies in eastern Tibet, including seismic anisotropy and seismicity detection. Crustal anisotropy are inversed according to shear-wave splitting of Pms phase from permanent station, and we observed that tectonic escaping, crustal flow, and crustal shortening may contribute to the tectonic evolution in various sub-areas in eastern Tibet. We also concentrated on the seismicity detection of 2013 Lushan earthquakes, and obtained details of the spatial and temporal aftershock evolution with the help of matched filter technique, suggesting that afterslip is the potential mechanism triggering Lushan aftershocks.

In order to understand more about eastern Tibet, we would keep on working in this area by focusing on the SKS, SKKS, PKS (hereafter, XKS phase) splitting and repeating earthquakes, which may reveal geodynamic processes in mantle and fault slip rate respectively.

Seismic hazard, for applications such as engineering structural design and insurance loss estimation, is represented as a probabilistic forecast. The most common form of seismic hazard representation is in the probability for a certain level of ground motion exceedance. The hazard also varies spatially, forming a hazard map.

As the amount of observation accumulates, recently there are more and more attempts to statistically evaluate the performance of probabilistic seismic hazard prediction using ground motion observations. This talk presents the general theory of this type of studies, using the United States Geological Survey National Seismic Hazard Maps as an example.