Abstract:In this paper, based on the seismicity and seismic structural analysis of the margin of the Bayan Har block, we discuss the risk of large earthquakes in the Maqu-Maqin seismic gap with regard to spatial seismicity patterns and temporal evolution of event sequences.According to paleo-earthquake and historical earthquake seismicities, there was an initial seismic gap at Maqu-Maqin along the east Kunlun fault, and therefore, large earthquakes will recur in this area.A second seismic gap, the seismic quiescence of no ML≥5.0 earthquakes, has been detected in the same area since 2008.A comparison with previous earthquake cases showed that a similar period of seismic quiescence formed in the region of Gansu-Qinghai-Sichuan provinces before the 1990 Gonghe M7.0 earthquake. The distribution of ML≥4.0 earthquakes in the current seismic quiescence is also similar to that of the Gonghe M7.0 case;hence, we think there is a risk of a large earthquake in the current gap.From the temporal sequences evolution analysis (M-T relations), we found that seismicity in the Gonghe gap had undergone strong-weak-strong stages prior to the Gonghe M7.0 earthquake. However, the seismicity in the current seismic gap in the region of Gansu-Qinghai-Sichuan provinces has also undergone the first two stages, and therefore, we conclude that it will soon reach the strong seismicity stage.We scanned the b-value distribution in this region, which showed that the b-values are very low around the east Kunlun fault and that there is locking in this area.We also calculated the spatial correlation lengths (SCL)and multiple fractal dimensions from the earthquake catalog of the Bayan Har block using GeoTaos.All the statistical seismicity parameters indicate that the risk of a large earthquake on the Maqu-Maqin segment of the east Kunlun fault is increasing, and therefore, researchers should monitor and study this area.
