In 1989, an unusual earthquake swarm occurred beneath Mammoth Mountain that was probably associated with magmatic intrusion. To improve our understanding of this swarm, we relocated Mammoth Mountain earthquakes using a double difference algorithm. Relocated hypocenters reveal that most earthquakes occurred on two structures, a near-vertical plane at 7–9 km depth that has been interpreted as an intruding dike, and a circular ring-like structure at ∼5.5 km depth, above the northern end of the inferred dike. Earthquakes on this newly discovered ring structure form a conical section that dips outward away from the aseismic interior. Fault-plane solutions indicate that in 1989 the seismicity ring was slipping as a ring-normal fault as the center of the mountain rose with respect to the surrounding crust. Seismicity migrated around the ring, away from the underlying dike at a rate of ∼0.4 km/month, suggesting that fluid movement triggered seismicity on the ring fault.
Citation Information
Publication Year | 2003 |
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Title | High precision earthquake locations reveal seismogenic structure beneath Mammoth Mountain, California |
DOI | 10.1029/2003GL018334 |
Authors | Stephanie G. Prejean, Anna Stork, William L. Ellsworth, David Hill, Bruce R. Julian |
Publication Type | Article |
Publication Subtype | Journal Article |
Series Title | Geophysical Research Letters |
Index ID | 70025055 |
Record Source | USGS Publications Warehouse |
USGS Organization | Alaska Science Center |