Reverse migration of seismicity on thrusts and normal faults

Graviquakes in Italy

“…9). In fact, normal faults rupture initiates at depth where the lithostatic load is maximum, and then propagates upward (Carminati et al, 2004). The results show that gravitational energy can generate earthquakes of magnitude comparable with the observed historic seismicity.…”

Intraplate stress state from finite element modelling: The southern border of the Spanish Central System

“…Though various authors suggest that the most appropriate nontectonic reference state of the lithosphere is that for which all three principal stresses are equal (Turcotte and Schubert, 1982;McGarr, 1988;Ranalli, 1995), several published works still discuss the approach of boundary condition of zero horizontal strain (Twiss and Moores, 1992;Engelder, 1993;Carminati et al, 2004). The most difficult component of the stress tensor to determine is the magnitude of maximum horizontal stress (Reynolds et al, 2006).…”

“…As a result, this issue remains still a subject of controversy in the scienti fic community (e.g. Carminati et al, 2004 ). On the other hand, in situ measurements in deep boreholes indicate higher horizontal than vertical stresses ( McGarr and Gay, 1978;Brudy et al, 1997;Reynolds et al, 2006 ), and both reference states represent, at best, incomplete approaches to lithospheric stresses.…”

Ruptures in a Highly Fractured Upper Crust

“…Besides, based on the analysis of shear-wave splitting beneath the Chiayi area, the source area of the Chiayi earthquake sequence also shows a high correlation with pore fluid pressure (CHEN and YEH, 1998). These results imply that the upward rupture process may have been caused by the occurrence of localized supra-lithostatic fluid pressure on the steeply inclined thrust fault, due to the inefficiency of hydro-fracturing (CARMINATI et al, 2004). On the basis of the above analysis, we conclude that the two earthquake sequences in our study area demonstrate common characteristics which include two distinct fault types for each sequence, the small volume of the aftershocks distribution especially for the Chiayi M 6.0 aftershock, short duration and substantial event scatter.…”