Rates of fluid expulsion across the northern Cascadia accretionary prism: Constraints from new heat flow and multichannel seismic reflection data
- Geological Survey of Canada, Sidney, British Columbia (Canada)
- Alfred Wegener Inst. fur Polar und Meerforschung, Bremerhaven (West Germany)
One hundred and ten closely spaced probe heat flwo measurements provide new constraints on the thermal regime of the northern Cascadia accretionary prism off Vancouver Island. Complementary heat flow values have been obtained from the depth of a bottom-simulating seismic reflector (BSR) that is interpreted to mark the thermally controlled base of a methane hydrate layer. The only local heat flow variations observed are associated with a sediment slump that is seen in SeaMARC II acoustic images and with the outcrop of several major thrust faults. Fluid expulsion resulting from the dewatering of the prism sediments appears to occur regionally in the 10-20-km-wide zone landward of the deformation front. In this area there is a significant disagreement between the probe and BSR heat flow estimates (roughly 30%) that can be explained by a regionally uniform vertical fluid flow at a rate of about 8 {times} 10{sup {minus}10} m/s. This is in good agreement with the estimated fluid expulsin rate required by the decrease in porosity landward of the deformation front, as estimated from the increase in seismic velocities derived from multichannel reflection data. The heat flow in Cascadia Basin seaward of the deformation front is in excellent agreement with that predicted by cooling plate models. Landward, there is a regional trend of decreasing heat flow across the accretionary prism, which is consistent with a model of simple tectonic thickening. Temperatures at the interface between the prism and the oceanic crust continue to increase landward, and reach 400-450 C beneath the middle to inner continental shelf. Initiation of megathrust earthquake failure along the main subduction thrust may be thus restricted by the high temperatures to the zone beneath the continental slope and outer shelf.
- OSTI ID:
- 5009110
- Journal Information:
- Journal of Geophysical Research; (United States), Vol. 95:B6; ISSN 0148-0227
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
03 NATURAL GAS
BRITISH COLUMBIA
SUBDUCTION ZONES
HEAT FLOW
HYDROLOGY
CONTINENTAL SHELF
DEFORMATION
EARTHQUAKES
FLUID FLOW
GAS HYDRATES
INTERSTITIAL WATER
METAMORPHISM
NATURAL GAS DEPOSITS
OCEANIC CRUST
PLATE TECTONICS
POROSITY
REFLECTIVITY
RESERVOIR FLUIDS
RESERVOIR TEMPERATURE
SEDIMENTARY BASINS
SEDIMENTS
SEISMIC SURVEYS
SEISMIC WAVES
WAVE PROPAGATION
CANADA
CONTINENTAL MARGIN
DEVELOPED COUNTRIES
EARTH CRUST
FLUIDS
GEOLOGIC DEPOSITS
GEOLOGIC STRUCTURES
GEOPHYSICAL SURVEYS
GROUND WATER
HYDRATES
HYDROGEN COMPOUNDS
MINERAL RESOURCES
NORTH AMERICA
OPTICAL PROPERTIES
OXYGEN COMPOUNDS
PHYSICAL PROPERTIES
RESOURCES
SEISMIC EVENTS
SURFACE PROPERTIES
SURVEYS
TECTONICS
WATER
580000* - Geosciences
030200 - Natural Gas- Reserves
Geology
& Exploration