Slip Distribution and Seismic Moment of the 2010 and 1960 Chilean Earthquakes Inferred from Tsunami Waveforms and Coastal Geodetic Data

摘要

The slip distribution and seismic moment of the 2010 and 1960 Chilean earthquakes were estimated from tsunami and coastal geodetic data. These two earthquakes generated transoceanic tsunamis, and the waveforms were recorded around the Pacific Ocean. In addition, coseismic coastal uplift and subsidence were measured around the source areas. For the 27 February 2010 Maule earthquake, inversion of the tsunami waveforms recorded at nearby coastal tide gauge and Deep Ocean Assessment and Reporting of Tsunamis (DART) stations combined with coastal geodetic data suggest two asperities: a northern one beneath the coast of Constitucion and a southern one around the Arauco Peninsula. The total fault length is approximately 400 km with seismic moment of 1.7 × 10~(22) Nm (Mw 8.8). The offshore DART tsunami waveforms require fault slips beneath the coasts, but the exact locations are better estimated by coastal geodetic data. The 22 May 1960 earthquake produced very large, ~30 m, slip off Valdivia. Joint inversion of tsunami waveforms, at tide gauge stations in South America, with coastal geodetic and leveling data shows total fault length of ~800 km and seismic moment of 7.2 × 10~(22) Nm (Mw 9.2). The seismic moment estimated from tsunami or joint inversion is similar to previous estimates from geodetic data, but much smaller than the results from seismic data analysis.