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Title: Seismomagnetic effect generated by the October 18, 1989, M sub L 7. 1 Loma Prieta, California, earthquake

Abstract

A differentially connected array of proton magnetometers operated within the epicentral region of the October 18, 1989, M{sub L} 7.1. Loma Prieta earthquake for 12 years from 1974 to 1986. The closest magnetometer station was located 7.3 km from the epicenter of the earthquake and within 3 km of the site where anomalous ULF magnetic noise measurements were observed. Following the earthquake, the magnetometers were reinstalled with sensors replaced in the original undisturbed sensor holders. Comparison of pre-1986 total intensity magnetic field data with data obtained during the months following the earthquake indicate local offsets of about 1 nT may have been generated at stations nearest the epicenter. Tests on other continuous differenced data from 1983 to present indicate that offsets determined could be biased by as much as 0.7 nT. The offsets can be approximately fit with a simple seismomagnetic model of the earthquake for which 1.9 m of right lateral and 1.3 m of dip slip (southwest side up) occurred on a fault patch between 6 km and 18 km deep and 45 km long. The total rock magnetization is assumed to be 1.5 A/m. Since the offset has persisted following the earthquake, an alternate explanation in termsmore » of electokinetic effects is unlikely even though transient ground water flow occurred following the earthquake. Comparison of pre-1986 and similar post-seismic total magnetic field noise does not indicate any change caused by aliasing of ULF (0.01 Hz-10 Hz) magnetic noise in the vicinity of the Loma Prieta earthquake.« less

Authors:
;  [1]
  1. Geological Survey, Menlo Park, CA (USA)
Publication Date:
OSTI Identifier:
6147987
Resource Type:
Journal Article
Journal Name:
Geophysical Research Letters (American Geophysical Union); (USA)
Additional Journal Information:
Journal Volume: 17:8; Journal ID: ISSN 0094-8276
Country of Publication:
United States
Language:
English
Subject:
58 GEOSCIENCES; CALIFORNIA; EARTHQUAKES; SEISMIC EFFECTS; MAGNETIC FIELDS; VARIATIONS; EPICENTERS; GEOLOGIC MODELS; MAGNETIC SURVEYS; MONITORING; FEDERAL REGION IX; GEOPHYSICAL SURVEYS; NORTH AMERICA; SEISMIC EVENTS; SURVEYS; USA; 580000* - Geosciences

Citation Formats

Mueller, R J, and Johnston, M J.S. Seismomagnetic effect generated by the October 18, 1989, M sub L 7. 1 Loma Prieta, California, earthquake. United States: N. p., 1990. Web. doi:10.1029/GL017i008p01231.
Mueller, R J, & Johnston, M J.S. Seismomagnetic effect generated by the October 18, 1989, M sub L 7. 1 Loma Prieta, California, earthquake. United States. https://doi.org/10.1029/GL017i008p01231
Mueller, R J, and Johnston, M J.S. 1990. "Seismomagnetic effect generated by the October 18, 1989, M sub L 7. 1 Loma Prieta, California, earthquake". United States. https://doi.org/10.1029/GL017i008p01231.
@article{osti_6147987,
title = {Seismomagnetic effect generated by the October 18, 1989, M sub L 7. 1 Loma Prieta, California, earthquake},
author = {Mueller, R J and Johnston, M J.S.},
abstractNote = {A differentially connected array of proton magnetometers operated within the epicentral region of the October 18, 1989, M{sub L} 7.1. Loma Prieta earthquake for 12 years from 1974 to 1986. The closest magnetometer station was located 7.3 km from the epicenter of the earthquake and within 3 km of the site where anomalous ULF magnetic noise measurements were observed. Following the earthquake, the magnetometers were reinstalled with sensors replaced in the original undisturbed sensor holders. Comparison of pre-1986 total intensity magnetic field data with data obtained during the months following the earthquake indicate local offsets of about 1 nT may have been generated at stations nearest the epicenter. Tests on other continuous differenced data from 1983 to present indicate that offsets determined could be biased by as much as 0.7 nT. The offsets can be approximately fit with a simple seismomagnetic model of the earthquake for which 1.9 m of right lateral and 1.3 m of dip slip (southwest side up) occurred on a fault patch between 6 km and 18 km deep and 45 km long. The total rock magnetization is assumed to be 1.5 A/m. Since the offset has persisted following the earthquake, an alternate explanation in terms of electokinetic effects is unlikely even though transient ground water flow occurred following the earthquake. Comparison of pre-1986 and similar post-seismic total magnetic field noise does not indicate any change caused by aliasing of ULF (0.01 Hz-10 Hz) magnetic noise in the vicinity of the Loma Prieta earthquake.},
doi = {10.1029/GL017i008p01231},
url = {https://www.osti.gov/biblio/6147987}, journal = {Geophysical Research Letters (American Geophysical Union); (USA)},
issn = {0094-8276},
number = ,
volume = 17:8,
place = {United States},
year = {Sun Jul 01 00:00:00 EDT 1990},
month = {Sun Jul 01 00:00:00 EDT 1990}
}