Zusammenfassung
The diverse aftershock sequence of the 1989 Loma Prieta earthquake
is inconsistent with conventional models of mainshock-aftershock
interaction because the aftershocks do not accommodate mainshock-induced
stress changes. Instead, the sense of slip of the aftershocks is
consistent with failure in response to a nearly uniaxial stress field
in which the maximum principal stress acts almost normal to the mainshock
fault plane. This orientation implies that (i) stress drop in the
mainshock was nearly complete, (ii) mainshock-induced decreases of
fault strength helped were important in controlling the occurrence
of after-shocks, and (iii) mainshock rupture was limited to those
sections of the fault with preexisting shear stress available to
drive fault slip.
Nutzer