WP2 — Enrichment of Existing Strong Motion Databases for Surface Wave Studies
Leader: Hideo Aochi (BRGM)
WP2 builds on the strong-motion database developed in the earlier ANR MODULATE project, which characterised basin-induced surface waves in the Los Angeles, Mexico City, Kanto and Nobi basins over a limited frequency band. IM-SURF extends this database along two axes: analysing recent major earthquakes to enrich it, and adopting stochastic and AI techniques to realistically predict high-frequency content that is coherent with the surface-wave components — most MODULATE signals were recorded with time steps too large to capture that high-frequency content.
Tasks
- Task 2.1 — Case study on recent earthquakes: analysis focuses on the 2023 Turkey earthquakes (Mw7.6 and Mw7.4), where more than ten stations within a few kilometres of the causal fault allow a complete near-field wave-field analysis, and on the 2024 Noto earthquake (Mw7.6, Japan), using high-quality data from the Japanese K-net and Kik-net networks.
- Task 2.2 — Hybrid ground motion generation in the presence of surface waves: stochastic methods generate the high-frequency content while the low-frequency part is calculated deterministically from the earthquake scenario and crustal structure. IM-SURF's novel approach uses the middle-frequency (body-wave) range to predict both the low-frequency (surface-wave) and high-frequency parts of the signal — a technique rarely applied in the presence of surface waves.
Milestones
- M2.1 — Report on post-processing of data from recent strong earthquakes
- M2.2 — Synthetic broad-band seismograms for the studied scenarios
Deliverables
- D2.1 — Report on the updated strong motion database, including new datasets from recent strong earthquakes
- D2.2 — Report on hybrid ground motion generation including surface waves