Changes in static stress on southern California faults after the 1992 Landers earthquake

Harris, Ruth; Simpson, Robert W.

doi:10.1038/360251a0

Cited by 268 publications

(166 citation statements)

References 17 publications

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“…The Big Bear cluster which is spatially separated from the main aftershock trend, may have resulted from the complex redistribution of stresses caused by the mainshock [Stein et al, 1992;Harris and Simpson, 1992]. It also exhibited mostly strike-slip deformation, left-lateral slip on northeast striking planes.…”

Section: Style Off Aultingmentioning

confidence: 99%

The 1992 Landers Earthquake Sequence: Seismological observations

Hauksson¹,

Jones²,

Hutton³

et al. 1993

J. Geophys. Res.

231

148

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The (MW6.1, 7.3, 6.2) 1992 Landers earthquakes began on April 23 with the MW6.1 1992 Joshua Tree preshock and form the most substantial earthquake sequence to occur in California in the last 40 years. This sequence ruptured almost 100 km of both surficial and concealed faults and caused aftershocks over an area 100 km wide by 180 km long. The faulting was predominantly strike slip and three main events in the sequence had unilateral rupture to the north away from the San Andreas fault. The MW6.1 Joshua Tree preshock at 33°N58′ and 116°W19′ on 0451 UT April 23 was preceded by a tightly clustered foreshock sequence (M≤4.6) beginning 2 hours before the mainshock and followed by a large aftershock sequence with more than 6000 aftershocks. The aftershocks extended along a northerly trend from about 10 km north of the San Andreas fault, northwest of Indio, to the east‐striking Pinto Mountain fault. The Mw7.3 Landers mainshock occurred at 34°N13′ and 116°W26′ at 1158 UT, June 28, 1992, and was preceded for 12 hours by 25 small M≤3 earthquakes at the mainshock epicenter. The distribution of more than 20,000 aftershocks, analyzed in this study, and short‐period focal mechanisms illuminate a complex sequence of faulting. The aftershocks extend 60 km to the north of the mainshock epicenter along a system of at least five different surficial faults, and 40 km to the south, crossing the Pinto Mountain fault through the Joshua Tree aftershock zone towards the San Andreas fault near Indio. The rupture initiated in the depth range of 3–6 km, similar to previous M∼5 earthquakes in the region, although the maximum depth of aftershocks is about 15 km. The mainshock focal mechanism showed right‐lateral strike‐slip faulting with a strike of N10°W on an almost vertical fault. The rupture formed an arclike zone well defined by both surficial faulting and aftershocks, with more westerly faulting to the north. This change in strike is accomplished by jumping across dilational jogs connecting surficial faults with strikes rotated progressively to the west. A 20‐km‐long linear cluster of aftershocks occurred 10–20 km north of Barstow, or 30–40 km north of the end of the mainshock rupture. The most prominent off‐fault aftershock cluster occurred 30 km to the west of the Landers mainshock. The largest aftershock was within this cluster, the Mw6.2 Big Bear aftershock occurring at 34°N10′ and 116°W49′ at 1505 UT June 28. It exhibited left‐lateral strike‐slip faulting on a northeast striking and steeply dipping plane. The Big Bear aftershocks form a linear trend extending 20 km to the northeast with a scattered distribution to the north. The Landers mainshock occurred near the southernmost extent of the Eastern California Shear Zone, an 80‐km‐wide, more than 400‐km‐long zone of deformation. This zone extends into the Death Valley region and accommodates about 10 to 20% of the plate motion between the Pacific and North American plates. The Joshua Tree preshock, its aftershocks, and Landers aftershocks form a previously missing link that connects...

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Section: Style Off Aultingmentioning

confidence: 99%

The 1992 Landers Earthquake Sequence: Seismological observations

Hauksson¹,

Jones²,

Hutton³

et al. 1993

J. Geophys. Res.

231

148

View full text Add to dashboard Cite

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“…The activation of an east-west aligned segment west of the main shock region (Figs 1 and 2) is likely to have been statically triggered by an increase of Coulomb failure stress (Decriem et al 2010). Comparable induced stress changes on adjacent faults have been suggested for a number of earthquakes including the SISZ 2000 earthquakes (Árnadóttir et al 2003) as well as the 1992 Landers M W 7.3 earthquake (Harris & Simpson 1992).…”

Section: Introductionmentioning

confidence: 99%

Temporal stress changes associated with the 2008 May 29M_W 6 earthquake doublet in the western South Iceland Seismic Zone

et al. 2015

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two magnitude M W ∼ 6 earthquakes occurred on two adjacent N-S faults in the western South Iceland Seismic Zone. The first main shock was followed approximately 3 s later by the rupture on a parallel fault, about 5 km to the west. An intense aftershock sequence was mostly confined to the western fault and an E-W aligned zone, extending west of the main shock region into the Reykjanes oblique rift. In this study, a total of 325 well-constrained focal mechanisms were obtained using data from the permanent Icelandic SIL seismic network and a temporary network promptly installed in the source region following the main shocks, which allowed a high-resolution stress inversion in short time intervals during the aftershock period. More than 800 additional focal mechanisms for the time period 2001-2009, obtained from the permanent SIL network, were analysed to study stress changes associated with the main shocks. Results reveal a coseismic counter-clockwise rotation of the maximum horizontal stress of 11 ± 10 • (95 per cent confidence level) in the main rupture region. From previous fault models obtained by inversion of geodetic data, we estimate a stress drop of about half of the background shear stress on the western fault. With a stress drop of 8-10 MPa, the pre-event shear stress is estimated to 16-20 MPa. The apparent weakness of the western fault may be caused by fault properties, pore fluid pressure and the vicinity of the fault to the western rift zone, but may also be due to the dynamic stress increase on the western fault by the rupture on the eastern fault. Further, a coseismic change of the stress regime-from normal faulting to strike-slip faulting-was observed at the northern end of the western fault. This change could be caused by stress heterogeneities, but may also be due to a southward shift in the location of the aftershocks as compared to prior events.

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“…[24] To calculate Coulomb stress, we follow the approach of King et al [1994] and Simpson and Reasenberg [1994] [also see Stein and Lisowski, 1983;Oppenheimer et al, 1988;Hudnut et al, 1989;Harris and Simpson, 1992]. The Coulomb failure criterion is…”

Section: Static Coulomb Stress and Seismic Moment Accumulationmentioning

confidence: 99%

Coulomb stress accumulation along the San Andreas Fault system

Smith

Sandwell

2003

J. Geophys. Res.

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[1] Stress accumulation rates along the primary segments of the San Andreas Fault system are computed using a three-dimensional (3-D) elastic half-space model with realistic fault geometry. The model is developed in the Fourier domain by solving for the response of an elastic half-space due to a point vector body force and analytically integrating the force from a locking depth to infinite depth. This approach is then applied to the San Andreas Fault system using published slip rates along 18 major fault strands of the fault zone. GPS-derived horizontal velocity measurements spanning the entire 1700 Â 200 km region are then used to solve for apparent locking depth along each primary fault segment. This simple model fits remarkably well (2.43 mm/yr RMS misfit), although some discrepancies occur in the Eastern California Shear Zone. The model also predicts vertical uplift and subsidence rates that are in agreement with independent geologic and geodetic estimates. In addition, shear and normal stresses along the major fault strands are used to compute Coulomb stress accumulation rate. As a result, we find earthquake recurrence intervals along the San Andreas Fault system to be inversely proportional to Coulomb stress accumulation rate, in agreement with typical coseismic stress drops of 1-10 MPa. This 3-D deformation model can ultimately be extended to include both time-dependent forcing and viscoelastic response.

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Changes in static stress on southern California faults after the 1992 Landers earthquake

Cited by 268 publications

References 17 publications

The 1992 Landers Earthquake Sequence: Seismological observations

The 1992 Landers Earthquake Sequence: Seismological observations

Temporal stress changes associated with the 2008 May 29M_W 6 earthquake doublet in the western South Iceland Seismic Zone

Coulomb stress accumulation along the San Andreas Fault system

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Changes in static stress on southern California faults after the 1992 Landers earthquake

Cited by 268 publications

References 17 publications

The 1992 Landers Earthquake Sequence: Seismological observations

The 1992 Landers Earthquake Sequence: Seismological observations

Temporal stress changes associated with the 2008 May 29MW 6 earthquake doublet in the western South Iceland Seismic Zone

Coulomb stress accumulation along the San Andreas Fault system

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Temporal stress changes associated with the 2008 May 29M_W 6 earthquake doublet in the western South Iceland Seismic Zone