Waveform inversion and analysis of an unusual earthquake swarm in the Boshan mining area, Shandong Province, China

Abstract

Moment tensor solutions were retrieved for the earthquake swarm that occurred during November and December 2010 in the Boshan mining area, Shandong Province, China. The results showed that the double-couple components in the source mechanisms were higher at the beginning of the swarm and consisted mainly of shear faulting controlled by tectonic stress. The subsequent events had significant non-double-couple components, indicating tensile faulting. The double-couple components predominately presented as normal faulting and the P axes were orientated almost vertically. The slip vectors of the swarm events were relatively stable. With reference to the tectonic features near the epicenter, we concluded that the swarm was a result of subordinate fault motion related to the Wangmu Mountain fault and that high-pressure pore fluids played a crucial role in the activity of the earthquake swarm.

Point‐Source Inversion of Small and Moderate Earthquakes From P‐wave Polarities and P/S Amplitude Ratios Within a Hierarchical Bayesian Framework: Implications for the Geysers Earthquakes

“…The time domain full waveform inversion has been widely used in moderate and large earthquakes (e.g., Dreger et al, ; Dziewonski et al, ; Minson & Dreger, ; Pasyanos et al, ; Romanowicz et al, ). It has also been used in small earthquake source inversion at short distances and high frequencies from mining activities (Fletcher & McGarr, ; Ma et al, ; Zheng et al, ) to geothermal earthquakes (Guilhem & Walter, ; Wang et al, ). While some other researchers carry out waveform inversion in frequency domain (e.g., Cesca et al, ; Dahm et al, ; Nakano et al, ; Romanowicz, ; Stump & Johnson, ), which is less sensitive to phase shifting and allows more stable solutions.…”