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

On January 11, 2018 (18:26 UTC), a Mw 6.0 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 stations, we refine the locations and moment tensors of the earthquake sequence. We relocate 98 earthquake epicenters and determine the focal mechanism and centroid depth of the mainshock and 20 aftershocks with Mw > 4. The relocated epicenters cluster in a NW‐SE direction that is consistent with the strike of the mainshock fault plane solution and the slip distribution derived from ALOS‐2 interferometric synthetic aperture radar observations. Most of the aftershocks have a pure thrust focal mechanism similar to the mainshock, except for four strike‐slip aftershocks. The refined locations and moment tensors of the thrust events clearly delineate a fault dipping ∼40° to the southwest at a depth range of 3–7 km, indicating that the earthquake sequence ruptured a previously unmapped, active fault. We interpret the earthquake sequence to be associated with pre‐existing faults within the BYR anticlinorium. This earthquake sequence and historical seismicity indicate that the upper crust of the BYR is highly stressed, resulting in ongoing distributed deformation between the oblique Rakhine megathrust and the dextral Sagaing Fault. The seismic hazard posed by these active faults has been increasing with the development of infrastructure such as dams within the BYR. Our study highlights the need for high‐resolution earthquake source parameter and strong ground motion attenuation studies for further understanding of the neotectonics of Myanmar and its related seismic hazard. Plain Language Summary: Myanmar is known to host many earthquakes, where most of the large earthquakes in the past have occurred along the strike‐slip Sagaing Fault and within the Indian plate that subducts beneath the Burma plate off the west coast of Myanmar. Less attention is given to smaller magnitude crustal earthquakes that occur in the region between the subduction zone and the Sagaing Fault, due to lack of instrumentation to detect these events and their less destructive potential. The 2018 Mw 6.0 earthquake occurred in this region within the Bago‐Yoma Range (BYR) and was not associated with any mapped active faults. We use seismological data, geodetic data, historical earthquake records, and published geologic surveys to study the earthquake sequence. We propose that the earthquake occurred on an existing shallow thrust fault within the BYR, which ruptured due to the region accommodating part of the compression associated with the subduction along multiple small‐scale crustal faults. We also highlight the increased seismic hazard in the region due to the close proximity of these active faults to numerous dams. Key Points: A Mw 6.0 earthquake ruptured a previously unmapped SW‐dipping thrust fault at shallow depths within the Bago‐Yoma Range (BYR) anticlinoriumThe upper crust of the Burma plate undergoes distributed deformation to partially accommodate the oblique convergence of the Indian plateThe proximity of mapped and potentially unidentified active faults within the BYR to dams indicate an increased seismic hazard [ABSTRACT FROM AUTHOR]