Lower-Crustal Rupture of the 1952 Mw 6.3 Suburban Pyongyang Earthquake: Insights into Seismogenic Reactivation in a Paleocollision Zone and Seismic Hazard Potential

ABSTRACT Characterizing historical earthquakes in low- to moderate-seismicity regions is critical for understanding long-term seismic hazard and tectonic evolution. Paleotectonic structures, such as reactivated fault zones formed during a paleocontinental collision, may still influence present-day seismic activity. We re-evaluate the 19 March 1952 suburban Pyongyang earthquake, the largest instrumentally recorded event in the Korean Peninsula, using long-period analog seismograms from far-regional and teleseismic stations. We use a multimethod approach that integrates long-period waveform inversion, depth-phase analysis, moment magnitude estimation, and synthetic waveform modeling. Our results constrain the focal depth to 29 (± 1) km, indicating rupture within the lower crust. The earthquake is characterized by a normal-faulting mechanism with a strike of 34°, dip of 66°, and rake of −103°, and moment magnitude of Mw 6.3 (Ms 6.2). Strong ground-motion simulations reproduce reported damage in Seoul (∼160 km from the epicenter) and estimate peak intensities of modified Mercalli intensity (MMI) IX near the epicenter and MMI VIII in central Pyongyang. Forward simulations of scenario earthquakes (Mw 5.0–7.0 and focal depths of 10–30 km) indicate the potential for significant ground shaking in the Pyongyang region. The 19 March 1952 suburban Pyongyang earthquake event provides insights into deep crustal deformation processes and active faulting mechanism, placing constraints on lower-crustal seismogenesis. The source region is inferred to lie along the eastern margin of a paleocollision zone between the North China and South China blocks, suggesting that inherited crustal structures remain capable of hosting damaging intraplate earthquakes.