第105回統計地震学セミナー / The 105th Statistical Seismology Seminar (Hybrid)

【Date＆Time】
20 August 2026　15:00-16:00
Admission Free, No Booking Necessary
【Place】
online (with zoom) and 4F Lounge (ISM)
Zoom meeting:
https://us06web.zoom.us/j/81029059041?pwd=jUmcFFxhQNTyK54KCitX5S7Yiax8t0.1
Meeting ID: 810 2905 9041
Passcode: 089990
【Speaker】
Dr. Ming-Che Hsieh (National Central University, Taiwan)
【Title】
Non-Ergodic Path Effects from 3-D Physics-Based Simulations of an M8 Ryukyu Earthquake in Eastern Taiwan
【Abstract】
The Ryukyu subduction zone offshore eastern Taiwan possesses significant seismogenic potential, exemplified by the 1920 earthquake. However, the scarcity of near-field observations leaves the ground motion characteristics of such mega-earthquakes poorly constrained, limiting the reliability of seismic hazard assessments. This study investigates long-period ground motion characteristics of a potential M8 Ryukyu earthquake using large-scale physics-based simulations. We simulated an M8 scenario earthquake using characterized source models based on the “Recipe” procedure and conducted 1,728 physics-based 3-D finite-difference simulations, incorporating variations in rupture nucleation, rupture velocity, source time function, asperity distribution, two tomographic velocity models, and topography. Synthetic waveforms were generated at 4,950 virtual stations, producing more than eight million synthetic ground motion records, and analyzed using RotD50 spectral accelerations (SA) at periods of 1.0, 3.0, and 5.0 s. Results indicate that rupture velocity and directivity dominate the spatial variability of long-period ground motions, with parameter sensitivity exhibiting strong spatial non-uniformity across the study region. Calibration against the empirical CH20 ground motion model suggests Gaussian source time functions of 2, 6, and 8 s provide the most consistent spectral representation for SA at 1.0, 3.0, and 5.0 s, respectively. The non-ergodic path terms (δP2P) derived from two independent velocity models reveal spatially consistent features, including a persistent amplification zone near Hualien linked to the Longitudinal Valley low-velocity structure, a de-amplification band along the Coastal Range and Central Range high-velocity material, and a frequency-dependent amplification in the Ilan Plain attributable to mid-to-deep crustal focusing or trapping rather than near-surface site effects. The workflow established here provides a transferable framework for refining ground motion models and advancing non-ergodic seismic hazard assessments in data-sparse subduction environments.