The October 17, 1989, Loma Prieta, California, Earthquake and its aftershocks: Geometry of the sequence from high-resolution locations

摘要: Hypocenters of the Loma Prieta sequence form a dipping zone that rises from mainshock hypocenter and is parallel to nodal plane. Most aftershocks cluster around perimeter zone, surrounding relatively aseismic center which approximates region rupture. At its southeastern end, aftershock warps into vertical surface corresponds San Andreas fault. In central northwestern parts at depths above ∼10 km, define numerous disjoint fault structures. The large component reverse-slip observed in this event agrees with simple model for slip on plane within compressional bend. We do not believe earthquake occurred Sargent However, we are unable conclude whether it ruptured principal plate boundary or less frequently active