Joint inversion of teleseismic body-wave data and strong ground motion waveforms was applied to determine the rupture process of the 2010 Mentawai earthquake. To obtain stable solutions, smoothing and non-negative constraints were introduced. A total of 33 teleseismic stations and 5 strong ground motion stations supplied data. The teleseismic and strong ground motion data were separately windowed for 150 s and 250 s and bandpass filtered with frequencies of 0.001e1.0 Hz and 0.005e0.5 Hz, respectively. The finitefault model was established with length and width of 190 km and 70 km, and the initial seismic source parameters were set by referring to centroid moment tensor(CMT) solutions. Joint inversion results indicate that the focal mechanism of this earthquake is thrust fault type, and the strike, dip, and rake angles are generally in accordance with CMT results. The seismic moment was determined as 5.814 1020Nm(Mw7.8) and source duration was about 102 s, which is greater than those of other earthquakes of similar magnitude. The rupture nucleated near the hypocenter and then propagated along the strike direction to the northwest, with a maximum slip of 3.9 m. Large uncertainties regarding the amount of slip retrieved using different inversion methods still exist; however, the conclusion that the majority of slip occurred far from the islands at very shallow depths was found to be robust. The 2010 Mentawai earthquake was categorized as a tsunami earthquake because of the long rupture duration and the generation of a tsunami much larger than was expected for an earthquake of its magnitude.
On 25 April, 2015, an Mw7.9 earthquake occurred in Nepal, which caused great economic loss and casualties. However, almost no surface ruptures were observed. Therefore, in order to interpret the phenomenon, we study the rupture process of the earthquake to seek answers. Inversion of teleseismic body-wave data is applied to estimate the rupture process of the 2015 Nepal earthquake. To obtain stable solutions, smoothing and non-negative constraints are introduced. 48 teleseismic stations with good coverage are chosen. Finite fault model is established with length and width of 195 km and 150 km, and we set the initial seismic source parameters referring to CMT solutions. Inversion results indicate that the focal mechanism of this earthquake is a thrust fault type, and the strike, dip and rake angle are in accordance with CMT results. The seismic moment is 0.9195 ×10^(21)Nm(Mw7.9), and source duration is about 70s. The rupture nucleated near the hypocenter and then propagated along the dip direction to the southeast, and the maximum slip amounts to 5.2 m. Uncertainties on the amount of slip retrieved by different inversion methods still exist, the overall characteristics are inconsistent. The lack of shallow slip during the 2015 Gorkha earthquake implies future seismic hazard and this region should be paid more attention to.
The Three Gorges Reservoir is a good site for the further researches on reservoir induced seismicity due to decades' seismic monitoring. After the first water impounding in 2003, seismic activity becomes more frequent than that before water impoundment. In order to quantitatively study, the relationship between the water level fluctuation and earthquakes in TGR, we introduced statistical methods to attain the goal.First of all, we relocated the earthquakes in TGR region with double difference method and divided the earthquakes into 5 clusters with clustering analysis method. Secondly, to examine the impacts of water level fluctuation in different water filling stages on the seismic activity in the 5 clusters, a series of statistical analyses are applied. Pearson correlation results show that only the 175 m water level fluctuation has significantly positive impacts on the seismic activity in clusters Ⅰ, Ⅱ, Ⅲ and Ⅴ with correlation coefficients of 0.44, 0.38, 0.66 and 0.63. Cross-correlation analysis demonstrates that 0, 1, 0 and 0 month time delay separately for the clusters Ⅰ, Ⅱ, Ⅲ and Ⅴ exists. It illustrated the influences of the water loading and pore pressure diffusion on induced earthquakes. Cointegration tests and impulse response analysis denoted that the 175 m water level only had long term and significant effects just on the seismic events in the intersection region of the Fairy Mount Fault and Nine-brook Fault. One standard deviation shock to175 m water level increased the seismic activity in cluster Ⅴ for the first 3 months, and then the negative influence was shown. After 7 months, the negative impulse response becomes stable. The long-term effect of the 175 m water impoundment also proved the important role of pore pressure diffusion in RIS with time.
