S U M M A R Y The wavelet approach to numerical simulation of elastic wave propagation is applied to models with localized heterogeneity, with significant contrasts with their surroundings. We consider zones with both lowered wave speed such as a fault gouge zone and elevated wave speeds such as in a subduction zone. In each of these situations the source lies within the heterogeneity. The repr...

The internal structure of a convergent plate boundary was the focus of ODP Leg 170 in 1996 at the subduction zone off Costa Rica. Although the structure of the subduction zone is rather well known from seismic surveys, prior to drilling of ODP Leg 170 it was a matter of discussion whether it is accretionary or non-accretionary. With a neural network approach, we confirm the evidence gained duri...

[1] Seismic reflection profiles shot across the Cascadia forearc show that a 5–15 km thick band of reflections, previously interpreted as a lower crustal shear zone above the subducting Juan de Fuca plate, extends into the upper mantle of the North American plate, reaching depths of at least 50 km. In the extreme western corner of the mantle wedge, these reflectors occur in rocks with P wave ve...

The supposed low viscosity of serpentine may strongly influence subduction-zone dynamics at all time scales, but until now its role could not be quantified because measurements relevant to intermediate-depth settings were lacking. Deformation experiments on the serpentine antigorite at high pressures and temperatures (1 to 4 gigapascals, 200 degrees to 500 degrees C) showed that the viscosity o...

Ruff, L.J., 1992. Asperity distributions and large earthquake occurrence in subduction zones. In: T. Mikumo, K. Aki, M. Ohnaka, L.J. Ruff and P.K.P. Spudich (Editors), Earthquake Source Physics and Earthquake Precursors. Tectonophysics. 211: 61-83. Plate tectonics and the seismic gap hypothesis provide the framework for long-term earthquake forecasting of plate boundary earthquakes. Unfortunate...

Most treatments of the Phanerozoic evolution of the carbon dioxide content of the atmosphere (PCO2 ) assume a steady state closed system. Release of CO2 by mantle degassing and by biogenic precipitation of carbonates and their metamorphism in subduction zones balances the consumption by continental aluminosilicate weathering. Small perturbations in this balance bring about changes in PCO2 , but...

The first of two tectonic-oriented objectives during Leg 160 in the Eastern Mediterranean Sea (April–May, 1995) was concerned with study of processes of genesis and incipient collision of the Eratosthenes Seamount, a substantial crustal feature, with the active margin of the Eurasian plate to the north, represented by southern Cyprus. The upper part of the Eratosthenes Seamount (upper several h...

Sediments tell a tsunami story Trying to understand where major earthquakes and tsunamis might occur requires analysis of the sediments pouring into a subduction zone. Thick sediments were expected to limit earthquake and tsunami size in the Sumatran megathrust event in 2004, but the magnitude 9.2 earthquake defied expectations. Hüpers et al. analyzed sediments recovered from the Sumatran megat...

For decades seismologists have sought causal relationships between maximum earthquake sizes and other properties of subduction zones, with the underlying notion that some subduction zones may never produce a magnitude ~9 or larger event. The 2004 Andaman Mw 9.2 earthquake called into question such ideas. Given multicentury return times of the greatest earthquakes, ignorance of those return time...