The 2016 Mw 5.9 Menyuan Earthquake in the Qilian Orogen, China: A Potentially Delayed Depth-Segmented Rupture Following from the 1986 Mw 6.0 Menyuan Earthquake

Abstract

An Mw 5.9 thrust earthquake occurred on 21 January 2016 in the northeastern Tibetan plateau, where another similar earthquake had ruptured in 1986. Because of the complexity and close proximity of multiple faults in this area, the exact causative fault sources for these two events have not previously been determined. We determined the seismogenic fault structural geometry of the 2016 event by analyzing the coseismic deformation from Sentinel-1A images, aftershock relocations, and geological data. Furthermore, field investigations and the relocated aftershocks for the 1986 event were used to investigate its seismogenic fault and relation with the 2016 Menyuan earthquake. The results indicate that the reverse slip of both events was distributed on the southwest-dipping Minyue-Damaying fault, where the 2016 event ruptured the deep segment and the 1986 event ruptured the shallow segment. We envision that the depth segmentation played an important role in the occurrence of two moderate earthquakes rupturing the same active fault but separated by almost 30 yr, which is thought much shorter than the average earthquake recurrence cycle. Our study indicates that seismic risks could be underestimated if depth segmentation is not considered.

Strain Partitioning on the Western Haiyuan Fault System Revealed by the Adjacent 2016 Mw5.9 and 2022 Mw6.7 Menyuan Earthquakes

“…The moment is 1.121 × 10 18 Nm (shear modulus 30 GPa, M w 5.97), slightly larger than the magnitude reported by the GCMT catalog ( M w 5.9). The derived slip distribution shows good data fitting between simulations and InSAR observations (Figure S2 in Supporting Information ) and is in line with previous InSAR studies (e.g., Li et al., 2016; Liu et al., 2018; Wang et al., 2017; Xiong et al., 2019; Zhang et al., 2020).…”

“…Given the simple surface deformation produced by the 2016 M w 5.9 earthquake (Figure 2a–2b and 2g–2h), a single plane is adequate to model its fault geometry, as shown in their small residues with single‐peak posterior probability distributions (Figures S1 and S2 in Supporting Information ). The optimal model indicates a thrust‐slip mechanism on a low‐angle, south‐dipping fault plane (strike = 122°, dip = 43°), similar to the source models from previous InSAR studies (e.g., Li et al., 2016; Liu et al., 2018; Wang et al., 2017; Xiong et al., 2019; Zhang et al., 2020).…”

“…A few studies have been conducted since the occurrence of the 2016 earthquake. Interestingly, previous studies suggest a purely thrust‐slip mechanism for the 2016 M w 5.9 event (e.g., Li et al., 2016; Liang et al., 2017; Wang et al., 2017; Zhang et al., 2020). The moment tensor solutions suggest a strike‐slip mechanism for the adjacent 2022 M w 6.7 earthquake (e.g., the USGS and Global Centroid Moment Tensor Catalog (GCMT) Ekström et al., 2012)).…”

Large‐Scale Interseismic Strain Mapping of the NE Tibetan Plateau From Sentinel‐1 Interferometry

“…However, considering that the fault patch that slipped during the earthquake was only 20 km long (Y. Li, Shan, et al., 2016; H. Wang et al., 2017), yet the high‐strain segment is three times longer indicates that the earthquake might have induced postseismic creep. The Menyuan Earthquake was a thrust earthquake that occurred on a fault splay attached to the Haiyuan Fault at a depth of 10 km (Y. Li, Jiang, et al., 2016; H. Wang et al., 2017; Y. Zhang et al., 2020). The motion of the pop‐up structure might have released normal stress on the Lenglengling Fault thus making stress conditions conducive to creep on the Haiyuan Fault.…”

Seismic Activities and Hazards of the Seismic Gaps in the Haiyuan Fault in Northeastern Tibet: Insights From Numerical Modeling Earthquake Interaction

“…Aftershocks relocation and earthquake rupture modeling studies revealed that this earthquake ruptured both eastern and western portions of TLSF and LLLF, respectively (Feng et al., 2022; Han, 2022; He et al., 2022; Liu, Zhuang, et al., 2022; Luo & Wang, 2022; LÜ et al., 2022; Peng et al., 2022; Xu et al., 2022; Zhu et al., 2022). The 2022 Menyuan earthquake is located approximately 30–40 km west to another two earlier Menyuan earthquakes (the 2016 Mw 5.9 and 1986 Mw 6.0 thrust earthquakes in the north LLLF and Minyue‐Damaying fault, respectively) (Peng et al., 2022; Yang et al., 2022; Zhang et al., 2020) (Figure 1). Peng et al.…”