The Elmore Ranch and Superstition Hills earthquakes of 24 November 1987: Introduction to the special issue

On 24 November 1987, two significant earthquakes occurred along the southern San Jacinto fault zone and related structural elements in southern California, not far from the International Border. These two events, the Elmore Ranch earthquake (M = 6.2 at 0154 GMT) and the Superstition Hills earthquake (M = 6.6 at 1315 GMT, both moment magnitudes from Sipkin, 1989), and their aftershocks have a rich harvest of geological, seismological, and engineering data pertinent to the cause and effect of earthquakes in this region, where the southern San Jacinto zone enters the Salton Depression from the Peninsula Ranges bordering it on the southwest (Fig. 1). This special issue of the Bulletin presents 18 geologic and seismologic investigations of these earthquakes, a collection of papers born in El Centro, California, on 8 and 9 February 1988 at a meeting attended by approximately 60 scientists interested in these earthquakes for one reason or another.