Abstract:
On September 5,2022, the Luding Earthquake triggered numerous landslides along the eastern and western edges of the Moxi elongated ice-water terrace in Sichuan,causing severe casualties and substantial economic losses. Understanding the seismic response characteristics and site effects of this elongated terrace is essential for clarifying the mechanisms and spatial distribution of landslides along the edges of such accumulation platforms during earthquakes. Using seismic data from the May 12,2023, Luding County
MS4.2 earthquake,we applied the horizontal-to-vertical response spectral ratio(HVSR)method to identify reference points for site-effect analysis. We then analyzed important duration(
D5~75),root-mean-square acceleration(
arms),continuous wavelet transforms,and horizontal polarization diagrams to examine time-domain and frequency-domain characteristics of the ground motion. The findings indicate: (1)Compared with the reference point(Monitoring Point 2 on valley bedrock),Monitoring Point 3 at the eastern edge of the terrace shows a pronounced topographic amplification effect in seismic amplitude,followed by Monitoring Point 1 on the left bank of the Yajiageng River. (2)As seismic waves propagate through the Moxi terrace,scattering generates waves in other frequency bands. (3)The eastern edge of the Moxi terrace exhibited multiple effects during this earthquake,including topographic amplification at slope breaks,medium amplification,and frequency-selective behavior of the accumulated material. This combination is referred to as the"ice-water terrace effect."Disaster prevention and mitigation planning in Moxi Town and similar settings should account for the potential hazards associated with this effect.