Discussion on moment tensor solution and seismogenic structure of Ruichang-Yangxin earthquake on 10 September 2011

Abstract

Ruichang-Yangxin earthquake is another moderate earthquake in Yangxin-Jiujiang area since 2005 Jiujiang-Ruichang M 5.7 earthquake. In order to more understand the seismic activities in this area, we study the moment tensor solution and the seismogenic structure of the Ruichang-Yangxin earthquake. Precise earthquake relocation shows that the mainshock occurred on the southwestern part of the NE-trending fault and aftershocks are distributed not only along the NE-trending fault but also along its conjugated NW-trending fault. By comprehensive analysis on the earthquake distribution, characteristics of isoseismal curve, focal mechanism, and regional structure characteristics, it is inferred that this earthquake is caused by the NE-trending Tanlu fault. In addition, it has close relationship with the conjugated NW-trending fault as well. Many researches have shown that the junction area is the earthquake-prone area, and should be paid more attention to. And our study also proves this viewpoint.

The 2020 M6.4 Jiashi Earthquake: An Event that Occurred Under the Décollement on the Kaping Fold-and-Thrust Belt in the Southwestern Tien Shan Mountains, China

“…In particular, the horizontal relocation errors in the longitudedirection generated by the R2 velocity model were far smaller than the vertical relocation errors. The relocation errors generated by the velocity models from Lü et al (2019), Song et al (2019), Huang et al (2006), and PE in CRUST2.0 were similar. Shown in Figure 8 is summary of the spatial distributions of aftershocks (the epicenters are the averages from the eight relocation results), with the relocation results color-coded by maximum and minimum depths (Figures 8A,B) and horizontal and vertical ranges (Figures 8C,D).…”

“…Below this region, approximately half of the shocks are at depths greater than 10 km; while above this region, the M L 1-3 shocks are at depths of 11-30 km. The hypocentral depths obtained using the DD relocation algorithm with the velocity model of Song et al (2019) are relatively shallow overall (basically less than 20 km) (Figure 4D), perhaps because this velocity model reflects influences from some localized structures. Specifically, the majority of the M L 1-3 shocks are relocated at depths shallower than 17 km.…”

“…In addition, in this model, the P-wave velocity (Vp) is relatively high at a depth of 10 km, gradually decreases at depths of 10-20 km, and gradually increases at depths greater than 22 km. (2) The velocity models used in the literature to determine the 2018 M5.5 Jiashi earthquake sequence, which occurred 45 km north of the 2020 Jiashi event (Song et al, 2019), was used. This velocity model is relatively refined and was obtained by inverting the data of earthquakes that occurred around from approximately 2009-2018.…”