
 We derive a new earthquake focal mechanism catalog for 86 Mw>4.0 earthquakes that occurred in the Myanmar region from 2016 to 2021. We apply the generalized Cut-and-Paste inversion method to a new set of regional broadband waveform data to obtain the earthquake focal mechanism and centroid depth with uncertainties estimated in a bootstrapping manner. Compared with global earthquake catalogs, our results are better aligned with mapped, active faults and reveal seismic activity along unmapped, blind faults. Our new catalog shows that the Sagaing Fault is more active in its northern segment with deeper seismogenic zone (∼27 km) compared to its southern segment that has a shallower seismogenic zone (∼10 km), sandwiching a seismic gap in its central segment. Earthquakes that occurred on the unmapped, blind faults beneath the Central Myanmar Basin at shallow depths (3–12 km) suggest a dominating northeast–southwest compressional stress field. Shallow earthquakes beneath the Indo-Myanmar Range (IMR) are rare, instead, north–south-oriented strike-slip faults are active within the deep accretionary wedge or lower crust of the Myanmar plate between depths of 20 and 40 km. At the eastern edge of the IMR, earthquakes with high-angle thrust mechanisms occurred between depths of 30 and 48 km, likely along steep faults separating the accretionary wedge from the Myanmar forearc crust. High-resolution intraslab focal mechanisms show that to the north of 22° N, slab deformation is dominated by strike-slip earthquakes with subvertical fault planes down to a depth of ∼25 km beneath the slab, suggesting lateral shear within the slab due to the northward motion of the Indian plate. To the south, more normal-faulting earthquakes suggest a stronger role of plate-bending processes in the slab deformation.

Active Faults Revealed and New Constraints on Their Seismogenic Depth from a High-Resolution Regional Focal Mechanism Catalog in Myanmar (2016–2021)

Ground Deformation and Source Fault Model of the Mw 5.7 Xegar (Tibetan Plateau) 2020 Earthquake, Based on InSAR Observation

Abstract Grid search is widely used in geophysical studies to determine model parameters that explain observed data. The residual between observed data and the model-predicted response, such as root mean square misfit, is usually used as a criterion to select the optimal model parameters. However, root mean square misfit is not a direct criterion for evaluating the reliability of a solution. In this study, we present a method to convert distributions of root mean square misfits obtained from a grid search into probability distributions to evaluate the results statistically based on a Bayesian framework. We applied the proposed method to synthetic geomagnetic anomaly datasets to evaluate the source position and magnitude of magnetic moments. The results are effectively visualized using marginal probability distributions for both well- and ill-posed problems, which are difficult for only root mean square misfits to evaluate. Then we applied the method to real geomagnetic anomaly data reflecting temporal magnetic variations due to volcanic activity in the Nishinoshima volcano. The resultant probability distributions indicate that the source must be in a narrow area northwest of the summit of the volcano with a large magnitude of demagnetization. The method is convenient and thus can be widely applied to multiple geophysical problems, including searches for the source locations of earthquakes, surface geodetic deformation, and magnetic change, and to their joint analyses. In addition, the method easily utilizes previous grid search results to evaluate the probability of model parameters. 

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Probability distributions of model parameters obtained by grid search – application to the geomagnetic anomaly source estimation problem

On 11 January 2018 (18:26 UTC), a Mw 60 earthquake occurred approximately 30 km west of the Sagaing Fault in the Bago-Yoma Range (BYR) Using a local broadband seismic network and regional seismic

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Wardah Fadil

Papers

The January 11, 2018, Mw 6.0 Bago-Yoma, Myanmar Earthquake: A Shallow Thrust Event Within the Deforming Bago-Yoma Range