Experimental characterization of seismic velocities in Nankai Trough samples
Abstract
We have performed tests to characterize the seismic velocities in samples collected in the Nankai Trough off the Kii Peninsula (Japan) during NanTroSEIZE stage 1. To reproduce in-situ conditions, we determined velocities in samples after applying both lithostatic and fluid pore pressure. The objective of these tests is threefold: First we aim at comparing these velocities, determined on a small scale (a few cm), with larger scale seismic velocities acquired either during logging or through seismic reflection studies. Second, we plan to study the dependence of seismic velocity on applied effective pressure, to estimate the possibility of tracking potential fluid overpressures. Finally, we aim at studying the variations in seismic properties within the prism, using the different cores, which were collected in very distinct domains of the accretionary prism. In particular, logging seismic velocity data acquired during campaign 314 (Tobin et al., 2008) show large variations between Site C0006, located near the frontal thrust and Sites C0001/C0002/C0004, located much landward near the out-of-sequence-thrust: for a given porosity, seismic velocities are much lower near the frontal thrust than in more internal domains of the prism. Starting from this observation, we characterize experimentally the extent of these variations and propose interpretation regarding the consolidation state and microstructure of accretionary prism sediments.
- Publication:
-
AGU Fall Meeting Abstracts
- Pub Date:
- December 2008
- Bibcode:
- 2008AGUFM.T31B1994R
- Keywords:
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- 0935 Seismic methods (3025;
- 7294);
- 3060 Subduction zone processes (1031;
- 3613;
- 8170;
- 8413);
- 5102 Acoustic properties;
- 7240 Subduction zones (1207;
- 1219;
- 1240)