How strong is an asperity

Journal Article · Sat May 01 04:00:00 EDT 1999 · Journal of Geophysical Research

DOI:https://doi.org/10.1029/1999JB900006· OSTI ID:355439

Sammis, C G ^[1]; Nadeau, R M; Johnson, L R ^[2]

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1. Department of Earth Sciences, University of Southern California, Los Angeles, California (United States)
2. Center for Computational Seismology, Lawrence Berkeley Laboratory and Seismographic Station and Berkeley Seismological Laboratory, University of California, Berkeley, California (United States)

A recent study of repeating earthquakes on the San Andreas Fault in central California by {ital Nadeau and Johnson} [1998] found that the smallest events occurred on patches having a linear dimension of the order of 0.5 m, displacements of about 2 cm, and stress drops of the order of 2000 MPa, roughly 10 times larger than rock strengths measured in the laboratory. The stress drop for larger events was observed to decrease as a power law of the seismic moment reaching the commonly observed value of 10 MPa at about magnitude 6. These large strengths are shown here to be consistent with laboratory data if the preexisting microcracks are all healed. A hierarchical fractal asperity model is presented, which is based on recent laboratory observations of contact distributions in sliding friction experiments. This {open_quotes}Cantor dust{close_quotes} model is shown to be consistent with the observed power law decrease in stress drop and increase in displacement with increasing event size. The spatial distribution of hypocenters in the Parkfield area is shown to be consistent with this simple fractal model and with a hierarchical clustering of asperities having a fractal dimension of D=1 and discrete rescaling factor of about 20. {copyright} 1999 American Geophysical Union

• OSTI ID: 355439
• Journal Information: Journal of Geophysical Research, Journal Name: Journal of Geophysical Research Journal Issue: B5 Vol. 104; ISSN JGREA2; ISSN 0148-0227
• Country of Publication: United States
• Language: English

Related Subjects

58 GEOSCIENCES
CRACKS
EARTHQUAKES
FRACTALS
GEOLOGIC FAULTS
ROCKS
SEISMOLOGY
STRESS ANALYSIS