The 1996 Peru tsunamigenic earthquake: Broadband source process

Abstract

Abstract. We investigate the spatio-temporal complexity of than a few tens of cm at various sites in the Pacific, the Marmoment release of the February 21, 1996 Peru earthquake quesas experienced locally water waves on the order of 2 m (M w 7.5). We use a non-linear source tomographic technique, [Heinrich et al., 1998]. We investigate the source process of based on simulated annealing, to invert surface wave source the 1996 Peru earthquake using two different methods: a) spectra for the slip distribution on a gently dipping fault plane. source tomography based on surface wave data that provide us The spectra (5-65 mHz) are obtained using an empirical with an appropriate low-frequency resolution of the source Green's function (EGF) method applied to first and second or-process (5-65 mHz), and an enhanced sensitivity to source dibit fundamental mode Rayleigh waves. Spectra are well fit by rectivity effects; b) inversion of broadband body waves to exa 110 km bilateral rupture, subparallel to the trench, updip of tend our analysis to higher frequencies (10-500 mHz). Our the hypocenter, with a total moment of 2.0x102ø Nm. The source tomographic model serves as a basis to calculate the non-linear inversion reveals a 30x30 km 2 major slip patch south the onset, where rupture velocities attain 1.5-2.0 km/s. Inversions of teleseismic broadband P and SH waves (10-500 mHz) indicate little or no directivity, consistent with the surface wave data. The average source time functions for both the surface and body wave data are similar in shape and in duration (-50 s). Part of the slip during the 1996 Peru event occurred in a region of reduced background seismicity, as was the case for the 1992 Nicaragua slow event, suggesting that the seismogenic potential of low seismicity regions near the trench should be globally reassessed.

Geodetic, teleseismic, and strong motion constraints on slip from recent southern Peru subduction zone earthquakes

“…There is a pattern of earthquake directivity along the coast of western South America (Figure 1). In the north, earthquakes rupture to the north (1979 M w 8.2 Colombia event [ Kanamori and Given , 1981; Beck and Ruff , 1984]), in the middle, earthquakes are bilateral (1996 M w 7.5 Peru earthquake [e.g., Ihmlé et al , 1998], the 1960 M w 7.6 Peru earthquake [ Pelayo and Wiens , 1990], and the 1966 M w 8.0 Peru event [ Beck and Ruff , 1989]), and south of about 12°S, directivity is southerly (the 1960 M w 9.5 Chile event [e.g., Benioff et al , 1961]; the 1974 M w 8.1 Peru event (bilateral, but most moment to south [ Langer and Spence , 1995]); and the 1985 M w 8.0 Chile event (ruptured updip and to the south [ Choy and Dewey , 1988; Mendoza et al , 1994]), as well as the 1995, 1996, and 2001 earthquakes). On the basis of these patterns, we hypothesize that the future rerupture of the 1877 earthquake will rupture to the south.…”

Radiated seismic energy and earthquake source duration variations from teleseismic source time functions for shallow subduction zone thrust earthquakes

“…We also estimate radiated seismic energy for tsunami earthquakes for which source time functions have been published. Six historic tsunami earthquakes believed to be associated with faulting rather than submarine slumps have been well studied with information on moment release history: 1946 Alaska [ Johnson and Satake , 1997], 1960 Peru [ Pelayo and Wiens , 1990], 1963 and 1975 Kurile [ Pelayo and Wiens , 1992], 1992 Nicaragua [ Ihmlé , 1996], 1996 Peru [ Ihmlé et al , 1998]. Our estimates of the radiated energy for the tsunami earthquakes use the duration and maximum moment rate from these published time functions (Figure 6).…”

Sources of Tsunami and Tsunamigenic Earthquakes in Subduction Zones

“…The rigidity for such a shallow fault may be small; if it is 1 × 10 10 N/m 2 , then the seismic moment becomes 3 × 10 20 Nm (M w 7.6), a value similar to the Harvard CMT solution. HEINRICH et al (1998) also modeled this tsunami on the basis of the seismic model of IHMLÉ et al (1998). Their source is also a shallow and narrow fault near the trench, although they concluded that the rigidity is 2 × 10 10 N/m 2 .…”