Precise Earthquake Relocation along the Egiin Davaa fault Hangay Dome, Central Mongolia
DOI:
https://doi.org/10.5564/pmas.v66i01.5340Keywords:
HypoDD, earthquake relocation, Egiin Davaa fault, Hangay Dome, Central Mongolia, seismogenic thickness, intracontinental deformation, seismic hazardAbstract
This study presents a precise earthquake relocation along the Egiin Davaa fault in the Hangay Dome, Central Mongolia, using the double-difference algorithm (HypoDD). We analysed 289 events from a dense temporary deployment of 72 broadband seismic station network (2012–2014), resulting in a high-quality catalogue of 253 events. The relocation achieved a 38% reduction in mean RMS residuals (to 0.34 s) and significantly improved precision (0.36 km horizontal, 0.68 km vertical), effectively eliminating artificial depth clustering artifacts. Our results reveal a sharply defined, near-vertical (80–90° dip) fault plane extending approximately 80 km at depth, confirming the Egiin Davaa fault as a mature, active seismogenic structure. Relocated hypocentres are distributed between 2 and 30 km, with the primary seismogenic thickness constrained to the upper 20–25 km. Notably, localised deepening to 30 km occurs near the Tsenkher hot spring (Profile C-C’). We suggest that high-pressure hydrothermal fluid migration along the fault reduces effective normal stress, facilitating brittle failure in the lower crust despite elevated regional heat flow (70–90 mW/m²). This study provides the first high-resolution constraints on the Egiin Davaa fault geometry and its seismogenic potential. By identifying the brittle-ductile transition at 20-25 km and quantifying the magnitude of potential strong earthquake is Mw 7.2 and more, the research significantly elevates the understanding of seismic hazards in Central Mongolia.
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