Abstract

The 18 October 1989 Loma Prieta earthquake (MS 7.1) provides unprecedented insights into geomorphological processes of the Santa Cruz Mountains region of central California. In particular, it inspires a simple explanation for the uplift that the area has been experiencing through its recent geological past. Predicted tectonic uplift from 442 oblique slip earthquakes on the Loma Prieta fault plane reproduces the variable elevations of 36 positions along the lowest Santa Cruz marine terrace within observational uncertainties. An inferred formation height of 8.9 ± 3 m ties the cutting of this terrace with the global sea level highstand at 125 Kyr B.P. Since then, uplift rates between 0.13 and 0.35 mm / yr have been maintained along the coast, about one third as fast as previously proposed. Loma Prieta-type earthquakes recur every three to six centuries and account for less than half of the strike-slip plate motion on this segment of the San Andreas. Repetition of these characteristic events over much longer periods likely explains the deformation of the older terraces and motivates the configuration of this portion of the coastal range.

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