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Spatial distribution and energy release of nonvolcanic tremor at Parkfield, California
Author(s) -
Staudenmaier Nadine,
Edwards Benjamin,
Tormann Thessa,
Zechar J. Douglas,
Wiemer Stefan
Publication year - 2016
Publication title -
journal of geophysical research: solid earth
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.983
H-Index - 232
eISSN - 2169-9356
pISSN - 2169-9313
DOI - 10.1002/2016jb013283
Subject(s) - seismology , moment magnitude scale , magnitude (astronomy) , attenuation , geology , range (aeronautics) , amplitude , moment (physics) , spatial distribution , fault (geology) , slipping , cluster (spacecraft) , energy (signal processing) , physics , statistics , geometry , computer science , remote sensing , materials science , mathematics , classical mechanics , quantum mechanics , astronomy , scaling , optics , composite material , programming language
Nonvolcanic tremors (NVTs) are observed in transition zones between freely slipping and locked sections of faults and normally occur below the seismogenic zone. Based on NVT recordings in the Parkfield region of the San Andreas Fault, we provide a novel approach to assess the energy release of these events and assign magnitudes ( M e ) that are compatible with size estimates of small earthquakes in the same region. To assess the energy magnitude of a detected tremor, we refine the estimate of its duration and perform a spectral analysis that accounts for local attenuation. For the 218 NVTs that we were able to process, we resolve M e values in the range of −0.67 to 0.84. For events, which we could not process using the spectral analysis technique, we propose a statistical model to estimate M e values using observable characteristics, such as peak amplitude, spectral velocity at the source corner frequency, and duration. We furthermore provide seismic moment and moment magnitude estimates and calculate stress drops in a range of 3–10 kPa. As a result of our spectral analyses, we find strong indications regarding the ongoing debate about potential NVT location hypotheses: the Parkfield NVTs have a higher probability to be located in the proposed three‐dimensional cloud‐like cluster than in any other suggested location distribution.