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The 2022 MW6.7 Menyuan earthquake ruptured the western end of the Tianzhu seismic gap, providing an opportunity to study the regional seismogenic characteristics and seismic hazards. Here we use interferometric synthetic aperture radar (InSAR) and seismic data to study the mainshock rupture, early afterslip and the second largest aftershock of the 2022 Menyuan earthquake sequences. Our modeling results show that the mainshock ruptured the Lenglongling fault and the Tuolaishan fault with a maximum slip of ~3 m. Rapid postseismic transient deformation occurred at the center of the Lenglongling fault. Our afterslip modeling reveals that the majority of afterslip occurred in the deeper part of the Lenglongling fault. A high-angle conjugated faulting event is found at the middle section of the Lenglongling fault. We use the stress inversion to investigate the possible triggering mechanism of the conjugated rupture event. The results indicate the maximum principal stress direction is in ~222°, forming a ~22° angle between the conjugated fault of second largest aftershock and the mainshock. The calculated normal stress changes indicate the region is within a pull-apart stress field, which favors such a conjugated rupturing event. Our study will help understand the rupture behavior of such kind of conjugated fault in other regions. [ABSTRACT FROM AUTHOR]

• The rupture process of the 2014 M w 6.2 Ludian earthquake was constrained by teleseismic data and more strong-motion data. • The Ludian earthquake ruptured two conjugate faults with strike angles of 77° and 160°, respectively. • The rupture simultaneously took place on two conjugate faults and lasted approximately 10 s. • The shallow dominating slip patch is the main reason for the enormous disaster from the earthquake source perspective. The M w 6.2 Ludian earthquake, struck Yunnan, China on August 3rd, 2014, leading to a complex aftershock distribution and enormous disaster. The Ludian earthquake is well recorded by the China Earthquake Network. The rupture process of the Ludian earthquake is constrained by the more local strong motion data including the LLT station with epicentral distance of ∼2 km and teleseismic body waves and surface waves in this study. The local strong motion data constrained the epicenter's location and rupture process better. Waveform fit of key local strong-motion stations supported that the Ludian earthquake ruptured two conjugate faults with strike angles of 77° and 160°, respectively. The rupture simultaneously took place on two conjugate faults and lasted approximately 10 s. The peak slip, rise time, and average slip rate are 0.63 m, 0.69 s, and 2.12 m/s, respectively. The result shows that the main rupture zone was on the fault with a strike of 160°. The depth of the major slip patch was 0–4 km with a centroid depth of 2 km. It indicates that the shallow slip is the main reason for the enormous disaster from the earthquake source perspective. [ABSTRACT FROM AUTHOR]

Abstract: Few building codes contains provisions fault surface ruptures and accompanying soil deformations which constitutes a great risk to human lives, buildings and infrastructure. A numerical and experimental comparison show a fair agreement of result. Analysis of “real” scale show the how water increases the incompressibility of wet soil causing shear deformations to become larger and conjugate ruptures to appear for reverse faults. Field observations and numerical analysis indicates that horizontal compression of soil surrounding underground structures should be taken into account in design. [Copyright &y& Elsevier]