Wide-band analysis of the 3 March 1985 central Chile earthquake: Overall source process and rupture history

Bulletin of the Seismological Society of America

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Abstract

We apply a linear, finite-fault waveform inversion scheme to the near-source strong-motion records, the teleseismic body waves, and the long-period Rayleigh waves recorded for the 3 March 1985 Chile earthquake to recover the mainshock rupture history. The data contain periods between about 2 and 350 sec and are inverted by allowing a variable dislocation rise time at each point on the fault. The results indicate that the mainshock had a seismic moment of 1.5 × 1028 dyne-cm (Mw 8.0) and ruptured mainly updip and to the south of the hypocenter for a distance of about 150 km along the Nazca-South America plate boundary. A smaller northward component of propagation is also evident, giving a total rupture length of about 200 km. The total source duration of the mainshock is 70 sec, with the majority of the slip occurring within the first 40 sec in a broad 100-km-wide zone in the northern half of the rupture area. Slip in this region extends from a depth of 55 km to within about 10 km of the surface and contains two areas of maximum slip (2.3 and 2.9 m) with rise times of approximately 14 sec. Slip in the southern portion of the fault reaches lower peak values (1.8 m) and extends downdip to depths no greater than 30 km. An independent variable rise-time inversion of the teleseismic body waves alone yields similar results, indicating that a significant component of slow fault motion is not required for this earthquake. The mainshock was preceded by several smaller precursors, the largest of which is an Mw ∼ 6.6 thrust earthquake occurring at a depth of 22 km in the shallow 15° dipping portion of the plate interface.

Additional publication details

Publication type Article
Publication Subtype Journal Article
Title Wide-band analysis of the 3 March 1985 central Chile earthquake: Overall source process and rupture history
Series title Bulletin of the Seismological Society of America
Volume 84
Issue 2
Year Published 1994
Language English
Publisher Seismological Society of America
Description 15 p.
First page 269
Last page 283