SEIZE Science Questions and Early Findings What controls the size of earthquakes on subduction thrusts? –What is the role of “asperities” – zones of high slips during earthquakes?

What controls the updip and downdip limits of the seismogenic zone of subduction thrusts?

How do stress, strain and pore fluid pressure vary through the earthquake cycle?

Correlated OBS and fluid flow results in Costa Rica (Brown and Schwarz)

Central America Smaller characteristic earthquakes (M~7-7.5) Temporal and spatially complex “patchy”patchy locking. with a limited slip distribution slow tsunamigenic earthquakes have occured off Nicaragua.

Nankai Larger magnitude (M~8-8.5) earthquakes, with relatively uniform fault properties and only small lateral changes large areas are fully locked most of the time

Connection to IODP drilling Costa Rica: two possible drilling locations proposed

NanTroSEIZE program at IODP Stage 1: 6 non-riser (shallow) sites Stage 2: Riser: NT2-03 to 3500 m; Non-Riser: Basement and monitoring of NT1-01 and NT1-07; monitoring and 2 nd borehole at NT2-01B, conducting active hydrological test; drill NT2-04 Stage 3: Riser NT3-01; possible deepening of NT1-03 Stage 4: Final observatories and monitoring

3D Seismic Survey April-May, 2006 M/V Nordic Explorer (PGS)

Chikyu Shakedown Early August-Oct 2006 Primarily to test equipment International scientists on board to provide lab input, learn more about Chikyu abilities