HR: 1330h
AN: S12A-0374    [PDF]
TI: Changes in hydrothermal activity and remotely triggered seismicity in Yellowstone National Park following the M7.9 Denali fault earthquake, Alaska
AU: * Husen, S
EM: shusen@mines.utah.edu
AF: Dept. of Geology and Geophysics, University of Utah, Salt Lake City, UT 84112 United States
AU: Taylor, R
EM: ralpht@iglou.com
AF: National Park Service, Yellowstone Center for Resources, Yellowstone National, WY 82190 United States
AU: Smith, R B
EM: rbsmith@mines.utah.edu
AF: Dept. of Geology and Geophysics, University of Utah, Salt Lake City, UT 84112 United States
AU: Heasler, H
EM: henry_heasler@contractor.nps.gov
AF: National Park Service, Yellowstone Center for Resources, Yellowstone National, WY 82190 United States
AB: The 2002 M7.9 Denali fault earthquake (DFE), Alaska, had a profound impact on the Yellowstone volcanic system despite the large distance of 3100 km. In this paper, we will report on changes in hydrothermal activity and triggered seismicity in Yellowstone following the DFE. We will also discuss possible mechanisms causing the observed changes and elaborate on a possible relationship between changes in hydrothermal activity and triggered seismicity. Following the DFE pronounced changes in the eruption behavior of several geysers in Yellowstone National Park were observed. For example, eruption intervals of Daisy Geyser located at Upper Geyser Basin dropped from 2.5 h prior to the Denali fault earthquake to 1.5 h after the Denali fault earthquake. In addition and coincident with the arrival of the large amplitude surface waves, intense earthquake swarms were remotely triggered throughout Yellowstone's major geyser basins. These observations can, in general, be explained by the interaction of large dynamic strains accompanying the DFE surface waves with hydrothermal fluids. Geyser eruption intervals are sensitive to conduit permeability and depth extent of the conduit suggesting that alteration of these two parameters caused the observed changes. A possible mechanism to increase the permeability of the geyser's conduit would be the removal of mineral seals due to dynamic stress changes associated with large amplitude surface waves. Opening of existing or new fractures at depth by intense earthquake swarm activity could increase conduit length, thus changing geyser eruption intervals. A number of mechanisms involving the interaction of hydrothermal fluids with large amplitude surface waves may have caused remote triggering of intense earthquake swarms close to Yellowstone's major geyser basins. These include rupturing of isolated compartments in which super-hydrostatic fluid pressure prevailed, the release of gas bubbles within hydrothermal fluids producing advective gas overpressure, and oscillation of gas bubbles within a saturated hydrothermal fluid increasing local pore pressure through rectified diffusion. The coincident occurrence of changes in hydrothermal activity and remotely triggered seismicity may suggest a causal relationship between the two. Unfortunately, the existing data is limited and we are not able to resolve whether there is a causal relationship between the two or changes in hydrothermal activity and triggered seismicity are just unrelated responses of a hydrothermal system to large amplitude surface waves.
DE: 7230 Seismicity and seismotectonics
DE: 7280 Volcano seismology (8419)
DE: 8424 Hydrothermal systems (8135)
SC: Seismology [S]
MN: 2003 Fall Meeting