scholarly journals Triggered slip along the San Andreas fault after the 8 July 1986 North Palm Springs earthquake

1988 ◽  
Vol 78 (3) ◽  
pp. 1112-1122
Author(s):  
Patrick L. Williams ◽  
Sally Fagerson McGill ◽  
Kerry E. Sieh ◽  
Clarence R. Allen ◽  
John N. Louie
Keyword(s):  
San Andreas Fault ◽  
Source Region ◽  
Slip Rate ◽  
Surface Cracks ◽  
Aseismic Slip ◽  
Imperial Valley ◽  
The North ◽  
San Andreas ◽  
Palm Springs ◽  
Lateral Displacements

Abstract In addition to minor surface cracks in the region of the 8 July 1986 North Palm Springs earthquake, minor aseismic surficial rupture occurred along three segments of the San Andreas fault, 44 to 86 km southeast of the epicenter. Data from a creepmeter and a tiltmeter at one locality suggest that triggered slip occurred coseismically beneath the instruments but took 33 hr to propagate to the surface. That slippage occurred coseismically at depth favors mechanisms for triggered slip that involve dynamic or static strain changes rather than creep migrating from the source region. The distribution of slip along the San Andreas fault associated with the North Palm Springs earthquake differed significantly from that recorded after the moderate 1968 Borrego Mountain, California and 1979 Imperial Valley, California, earthquakes. During these earthquakes, triggered slip occurred along the San Andreas fault in the Durmid Hill area and in the Mecca Hills. Triggered slip associated with the North Palm Springs earthquake occurred in these two areas again, but also extended farther northwest into the Indio Hills, where as much as 9 mm of dextral slip occurred. In the Mecca Hills, surface cracks in 1986 appeared over a shorter fault length than in previous events, and the dextral displacement was smaller, with maximum values of only 2 to 3 mm. On Durmid Hill, surface cracks in 1986 were localized along a 200-m-long stretch of the fault spanning the Mecca Beach creepmeter and extending about 150 m to the southeast. Right-lateral displacements on surface cracks in this area were 1.4 to 2.0 mm, smaller than those observed in previous events. Although the mechanism of triggered aseismic slip is poorly understood, examination of displacement rates for the past several decades to centuries may indicate whether the aseismic slip rate is constant or represents accelerating premonitory failiure of the southernmost San Andreas fault.

Reconstructing 10 years of spatio-temporal aseismic slip history along the San Andreas Fault

2020 ◽  
Author(s):  
Sylvain Michel ◽  
Romain Jolivet ◽  
Adriano Gualandi ◽  
Blandine Guardonio ◽  
Olivier Lengliné ◽  
...  
Keyword(s):  
San Andreas Fault ◽  
Slip Rate ◽  
Temporal Variations ◽  
Independent Component ◽  
Tectonic Activity ◽  
Aseismic Slip ◽  
Linear Inversion ◽  
San Andreas ◽  
Acceleration And Deceleration ◽  
Spatio Temporal

<p>The San Andreas Fault creeping section is generally considered as slipping continuously and aseismically, at a rate of about 35 mm/yr. However, recent studies, using either Global Positioning System (GPS) network or Interferometric Synthetic Aperture Radar (InSAR) data, have highlighted spatial and temporal variations of slip rate. Here, we combine GPS, InSAR, creepmeter and seismicity data over the 2008-2018 period, taking advantage of their complementary spatial and temporal resolutions, to detail a comprehensive picture of episodic acceleration and deceleration slip patterns. For this purpose, we use a variational Bayesian Independent Component Analysis (vbICA) decomposition to separate geodetic deformation due to non-tectonic sources from signals of tectonic origin. The fault slip kinematics is reconstructed by linear inversion of each Independent Component related to transient tectonic activity. We document aseismic slip acceleration transients and discuss their origin.</p>

Identifying 2000 small and large creep events on the San Andreas Fault.

2021 ◽  
Author(s):  
Daniel Gittins ◽  
Jessica Hawthorne
Keyword(s):  
Cross Correlation ◽  
San Andreas Fault ◽  
Slip Rate ◽  
Automated Detection ◽  
Seismogenic Zone ◽  
Near Surface ◽  
The North ◽  
San Andreas ◽  
Continuous Background

<p>The San Andreas fault has been observed to creep at the surface along the 175km section between San Juan Bautista and Cholame (Titus et al., 2011). This section is known as the creeping section and accumulates slip in two modes: during continuous background slip at a long term slip rate and in accelerated slip bursts known as creep events (Gladwin et al., 1994). But the size and importance of creep events remain unclear. Some researchers treat them as small, ~100-m-wide near-surface events (Gladwin et al., 1994), but others suggest that many creep events reach 4 km depth, connecting the surface to the seismogenic zone (Bilham et al., 2016). So, in this study, we systematically characterize the along-strike rupture extents of creep events along the San Andreas Fault, to determine if these are small, localized phenomena or large, segment-rupturing events.</p><p>We detect creep events and analyse their propagation using 18 USGS creepmeter records from the San Andreas Fault. Each creepmeter operated for at least 9 of the years between 1985 and 2020. To begin we systematically detect creep events using a cross-correlation approach. We identify periods that have significant slip and signals with high similarity to a template creep event. This automated detection allows us to produce a catalogue with 2000 creep events. The method detects at least 95% of the creep events identified by visual inspection.</p><p>Once we have found creep events at each creepmeter, we examine how creep events propagate. We compare creep event detections between pairs of creepmeters to determine how many creep events propagate from one creepmeter to the other. At the northern end of the creeping section, we observe that 18-28% of the creep events found at Harris Ranch are also found at Cienega Winery within 24hrs. This coincident timing implies that 18-28% of creep events in the north have an along-strike length of at least 4 km. Many creep events at the southern end of the creeping section appear to be even larger. For instance, a few events appear to be at least 31 km long; 10-38% of creep events at Slacks Canyon also observed at Work Ranch (31 km away) within 24hrs. These large along-strike rupture extents imply that creep events connect the slip and stress field over large regions of the San Andreas Fault. These events may play an important role in the slip dynamics of the creeping section.</p>

scholarly journals A revised position for the primary strand of the Pleistocene-Holocene San Andreas fault in southern California

2021 ◽  
Vol 7 (13) ◽  
pp. eaaz5691
Author(s):  
Kimberly Blisniuk ◽  
Katherine Scharer ◽  
Warren D. Sharp ◽  
Roland Burgmann ◽  
Colin Amos ◽  
...  
Keyword(s):  
Los Angeles ◽  
Southern California ◽  
San Andreas Fault ◽  
Slip Rate ◽  
Large Magnitude ◽  
Slip Rates ◽  
San Andreas ◽  
The Pacific ◽  
Large Earthquakes ◽  
Dependent Probability

The San Andreas fault has the highest calculated time-dependent probability for large-magnitude earthquakes in southern California. However, where the fault is multistranded east of the Los Angeles metropolitan area, it has been uncertain which strand has the fastest slip rate and, therefore, which has the highest probability of a destructive earthquake. Reconstruction of offset Pleistocene-Holocene landforms dated using the uranium-thorium soil carbonate and beryllium-10 surface exposure techniques indicates slip rates of 24.1 ± 3 millimeter per year for the San Andreas fault, with 21.6 ± 2 and 2.5 ± 1 millimeters per year for the Mission Creek and Banning strands, respectively. These data establish the Mission Creek strand as the primary fault bounding the Pacific and North American plates at this latitude and imply that 6 to 9 meters of elastic strain has accumulated along the fault since the most recent surface-rupturing earthquake, highlighting the potential for large earthquakes along this strand.

scholarly journals Aseismic slip and seismogenic coupling along the central San Andreas Fault

2015 ◽  
Vol 42 (2) ◽  
pp. 297-306 ◽  
Author(s):  
R. Jolivet ◽  
M. Simons ◽  
P. S. Agram ◽  
Z. Duputel ◽  
Z.-K. Shen
Keyword(s):  
San Andreas Fault ◽  
Aseismic Slip ◽  
San Andreas

scholarly journals New geodetic constraints on southern San Andreas fault-slip rates, San Gorgonio Pass, California

Geosphere ◽  
2020 ◽  
Author(s):  
Katherine A. Guns ◽  
Richard A Bennett ◽  
Joshua C. Spinler ◽  
Sally F. McGill
Keyword(s):  
Velocity Field ◽  
Southern California ◽  
San Andreas Fault ◽  
Plate Boundary ◽  
Slip Rate ◽  
Fault Slip ◽  
Slip Rates ◽  
San Andreas ◽  
Fault Slip Rates ◽  
Gps Velocity Field

Assessing fault-slip rates in diffuse plate boundary systems such as the San Andreas fault in southern California is critical both to characterize seis­mic hazards and to understand how different fault strands work together to accommodate plate boundary motion. In places such as San Gorgonio Pass, the geometric complexity of numerous fault strands interacting in a small area adds an extra obstacle to understanding the rupture potential and behavior of each individual fault. To better understand partitioning of fault-slip rates in this region, we build a new set of elastic fault-block models that test 16 different model fault geometries for the area. These models build on previ­ous studies by incorporating updated campaign GPS measurements from the San Bernardino Mountains and Eastern Transverse Ranges into a newly calculated GPS velocity field that has been removed of long- and short-term postseismic displacements from 12 past large-magnitude earthquakes to estimate model fault-slip rates. Using this postseismic-reduced GPS velocity field produces a best- fitting model geometry that resolves the long-standing geologic-geodetic slip-rate discrepancy in the Eastern California shear zone when off-fault deformation is taken into account, yielding a summed slip rate of 7.2 ± 2.8 mm/yr. Our models indicate that two active strands of the San Andreas system in San Gorgonio Pass are needed to produce sufficiently low geodetic dextral slip rates to match geologic observations. Lastly, results suggest that postseismic deformation may have more of a role to play in affecting the loading of faults in southern California than previously thought.

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