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Possible tectonomagnetic effect observed from mid-1989, to mid-1990, in Long Valley Caldera, California

Geophysical Research Letters

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Abstract

Precise measurements of local magnetic fields have been obtained with a differentially connected array of three proton magnetometers in the Long Valley Caldera region since 1984. After correction for secular variation, it is apparent that an anomalous 2 nT decrease in the magnetic field occurred from mid-1989 to mid-1990 at the magnetometer located closed to the center of the resurgent dome inside the caldera. During this period a significant increase in geodetic strain rate of 8.5 ppm/a was observed on the two-color geodimeter network within the caldera from October, 1989, to mid-1990 and a dramatic increase in seismic activity occurred from December, 1989 to July, 1990. A simple dilatational point-source model with pressure increasing by 52 Mpa from October 1989 to August 1990 at a depth of about 7 km beneath the center of the resurgent dome can be fit to the strain data. Magnetic, seismic and geodetic data suggest that an episode of active magmatic intrusion occurred from late 1989 to mid-1990 at a depth of about 7-8 km beneath the resurgent dome within the caldera. -from Authors

Additional Publication Details

Publication type:
Article
Publication Subtype:
Journal Article
Title:
Possible tectonomagnetic effect observed from mid-1989, to mid-1990, in Long Valley Caldera, California
Series title:
Geophysical Research Letters
Volume
18
Issue:
4
Year Published:
1991
Language:
English
Larger Work Type:
Article
Larger Work Subtype:
Journal Article
Larger Work Title:
Geophysical Research Letters
First page:
601
Last page:
604
Number of Pages:
4