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Titolo:
Fluid pressures at hypocenters of moderate to large earthquakes
Autore:
Streit, JE; Cox, SF;
Indirizzi:
Australian Natl Univ, Dept Geol, Canberra, ACT 0200, Australia Australian Natl Univ Canberra ACT Australia 0200 rra, ACT 0200, Australia Australian Natl Univ, Res Sch Earth Sci, Canberra, ACT, Australia Australian Natl Univ Canberra ACT Australia ci, Canberra, ACT, Australia
Titolo Testata:
JOURNAL OF GEOPHYSICAL RESEARCH-SOLID EARTH
fascicolo: B2, volume: 106, anno: 2001,
pagine: 2235 - 2243
SICI:
0148-0227(20010210)106:B2<2235:FPAHOM>2.0.ZU;2-C
Fonte:
ISI
Lingua:
ENG
Soggetto:
SAN-ANDREAS FAULT; RECRYSTALLIZED GRAIN-SIZE; VALVE BEHAVIOR; RUPTURE NUCLEATION; CONTINENTAL-CRUST; UNITED-STATES; SHEAR-STRESS; FLOW LAWS; QUARTZ; STRENGTH;
Tipo documento:
Article
Natura:
Periodico
Settore Disciplinare:
Physical, Chemical & Earth Sciences
Citazioni:
60
Recensione:
Indirizzi per estratti:
Indirizzo: Streit, JE Univ Adelaide, Natl Ctr Petr Geol & Geophys, Thebarton Campus, Adelaide, SA 5005, Australia Univ Adelaide Thebarton Campus Adelaide SA Australia 5005 ralia
Citazione:
J.E. Streit e S.F. Cox, "Fluid pressures at hypocenters of moderate to large earthquakes", J GEO R-SOL, 106(B2), 2001, pp. 2235-2243

Abstract

Many active faults are expected to develop fluid pressures in excess of hydrostatic pressures below 3 to 7 km depth during interseismic periods. Suprahydrostatic fluid pressures are known to reduce the stresses required for brittle failure. Stress differences that trigger moderate to large earthquakes typically range from 40 to 160 MPa, as indicated by earthquake shear stress drops and paleostress estimates obtained from mylonites. For stresses in this range (40-160 MPa), seismic fault reactivation requires in most cases pore fluid factors (fluid pressure/overburden pressure) higher than for hydrostatic fluid pressures (i.e., >0.37) along misoriented faults with fault angles greater than or equal to 45 degrees, such as many segments of theSan Andreas fault system. For example, at a stress difference of 100 MPa and fault angles of 45 degrees - 55 degrees, fault reactivation at 7 to 20 km depth requires hypocentral pore fluid factors of approximate to0.8-1 for reverse faults, 0.6-0.9 for strike-slip faults, and <0.8 for normal faults. Pore fluid factors increase with increasing cohesive strength of faults, increasing coefficient of internal friction, and increasing fault angle. Seismic reactivation of cohesive faults at stress differences of 40-160 MPa requires near the base of the seismogenic zone (<approximate to>15 km depth) suprahydrostatic fluid pressures at all possible fault angles. Pore fluid factors are approximate to0.4-0.9 for normal faults, approximate to0.6-1 forstrike-slip faults, and approximate to0.8-1.05 for thrust or reverse faults. These constraints are potentially useful for the modelling of seismic faulting and earthquake recurrence times.

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Documento generato il 29/09/20 alle ore 23:49:44