The Bayesian inversion framework is a powerful framework for solving nonlinear inversion problems, but its application to fault slip inversion is often hindered by high computational costs. In this study, we propose a new approach that approximates the spatial-domain slip distribution using only its low-frequency components in the frequency-domain. This strategy substantially reduces the number of model parameters under the physically reasonable assumption that coseismic slip distributions are smooth and dominated by low-frequency features. We evaluate the method using three synthetic fault slip models with different characteristics, demonstrating that it achieves high data-fitting accuracy with markedly improved computational efficiency. When applied to the 1973 MS7.5 Luhuo (China) earthquake, our approach yields a coseismic slip model that broadly agrees with previous studies in its first-order features, while differences in small-scale details likely reflect variations in the dataset used. This work demonstrates an efficient and robust strategy for Bayesian coseismic slip inversion, enabling broader applications in earthquake source studies.

The vertical component of surface afterslip of the 2008 Mw7.9 Wenchuan Earthquake, China, has been observed since 2011 using repeated levelings at the Yingxiu site, which spans the southwestern segment of the 2008 rupture. We present the geological, co-seismic rupture, and aftershock features around the Yingxiu site and employ the rate- and state-dependent friction theory to analyze the friction mechanism and depth of the afterslip. The logarithmically increasing afterslip series with a cumulative amount of -30 mm obeys a velocitystrengthening friction law, from which the afterslip depth is estimated to be 2.6-6 km. This depth is further constrained to -5 km that probably represents the thickness of a shallow velocity-strengthening layer of the fault, from information of sedimentary strata and aftershock distribution. The coseismic reverse vertical slip was <3 m around the Yingxiu site during the 2008 mainshock, whereas that on the adjacent rupture section to the northeast was >= 8 m above -15 km depth, including the largest slip of 12.5 m at -13 km depth (Zhang et al., 2012). These features suggest that an apparent deficit of coseismic slip existed on the rupture section at the Yingxiu site, compared with coseismic slip on the adjacent section. Furthermore, the surface-observed afterslip is uncorrelated with the aftershock slip on the fault in the underlying velocity-weakening layer. Therefore, the surface afterslip at the Yingxiu site is due to post-2008 relaxation that compensates for the coseismic slip deficit in the shallow layer of the fault and is probably governed by velocity-strengthening friction.

Before the Lushan M7. 0 earthquake of April 20,2013,fault displacement time histories inferred from near-field observation in Xianshuihe,Anninghe and Zemuhe Fault zones in Sichuan Province showed long-,mid-,and short-term anomalies which deviated from the normal background. The longterm anomalies were mainly represented by extensional faulting,the mid-term anomalies were marked mainly by turning of anomaly trends,and the short-term anomalies appeared mainly as compressional movement of the central-northern segment of Xianshuihe Fault. And based on these anomalies,a relatively accurate short-term prediction to this earthquake was proposed by the Survey Engineering Institute of Earthquake Administration of Sichuan Province. In this article,we summarize the thoughts and process of the prediction to Lushan earthquake,and present the bases and process for the long-,mid-,and short-term prediction. This experience can be useful for short-term prediction of strong earthquake in the future. Our preliminary results show that: 1) The sudden acceleration of variation in anomaly of short-baseline and short-leveling has short-term predictive significance to the origin time of strong earthquake. 2) Combined with analysis on the characteristics of time series of the occurrence time of cross-fault deformation anomalies,and the high gradient zones and their temporal evolutions revealed by mobile gravity surveys,we chose the intersection of the anomalous zones as the hazardous area and found it has a better predictive effect for determining the location of strong earthquake. 3)Statistical analysis shows that the duration of cross-fault deformation anomalies has certain significance for predicting the magnitude of strong earthquake. According to the characteristics of fault activity,the southeastward movement rate of the Bayar Har block may be greater than that of the eastern boundary of the Sichuan-Yunnan block before the Lushan earthquake, which aggravated the compressional and extensional movement of the northern segment of Longmenshan Fault,the middlenorthern segment of Xianshuihe Fault and the Zemuhe Fault,and made the southern segment of Longmenshan Fault and the northern segment of Anninghe Fault locked. The faults differed remarkably in their activity patterns, which were mutually restrained and adjusted, as well as convertible. Thus,brittle rocks in the transition zone between plateau and basin ruptured and earthquake occurred. Currently,short-term earthquake prediction is still based on empirical results,and its scientificity is insufficient and pending further discussion.