California Earthquakes: Why Only Shallow Focus?

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Science  26 Jun 1970:
Vol. 168, Issue 3939, pp. 1573-1575
DOI: 10.1126/science.168.3939.1573


Frictional sliding on sawcuts and faults in laboratory samples of granite and gabbro is markedly temperature-dependent. At pressures from 1 to 5 kilobars, stick-slip gave way to stable sliding as temperature was increased from 200 to 500 degrees Celsius. Increased temperature with depth could thus cause the abrupt disappearance of earthquakes noted at shallow depths in California.

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