Geodetic measurements of postseismic crustal deformation following the 1979 Imperial Valley earthquake, California

1983 ◽  
Vol 73 (4) ◽  
pp. 1203-1224
Author(s):  
J. Langbein ◽  
A. McGarr ◽  
M. J. S. Johnston ◽  
P. W. Harsh
Keyword(s):  
Crustal Deformation ◽  
Main Shock ◽  
Average Rate ◽  
Fault Slip ◽  
Lake Basin ◽  
East Side ◽  
Observational Period ◽  
Imperial Valley ◽  
Array Measurements ◽  
Postseismic Slip

abstract A geodetic trilateration network comprising 54 baselines was established around the northern part of the Imperial fault beginning 12 days after the Imperial Valley earthquake of 15 October 1979, and the line lengths were repeatedly observed during the following 110 days. During the observational period, there was an average of about 10 cm of dextral postseismic fault slip. Geodetic data in conjunction with alignment-array measurements indicate that the postseismic slip U at time t following the main shock is well described by U (t) = (10.96 ± 0.12) cm log(t/1.75 day + 1), a result that implies that it will be approximately 9 to 10 yr before the rate of postseismic displacement diminishes to the ambient rate of creep of 0.5 cm/a. The postseismic strain changes are localized to the east side of the Imperial fault in the southern part of the Mesquite Lake basin, where significant north-south extension occurred at an average rate of 2.7 ± 0.3 × 10−5/a during the observational period. These changes are compatible with dextral fault slip within the top 5 km of the fault.

Direct observation of rupture propagation during the 1979 Imperial Valley earthquake using a short baseline accelerometer array

1984 ◽  
Vol 74 (6) ◽  
pp. 2083-2114
Author(s):  
Paul Spudich ◽  
Edward Cranswick
Keyword(s):  
Seismic Waves ◽  
Main Shock ◽  
Ground Motions ◽  
P Wave ◽  
Time Base ◽  
Correlation Technique ◽  
Imperial Valley ◽  
Short Baseline ◽  
Fault Surface ◽  
S Waves

Abstract The 1979 Imperial Valley, California, earthquake (Ms = 6.9) was recorded on the El Centro differential array, a 213-m-long linear array of 5 three-component digital accelerometers 5.6 km from the nearest tectonic surface rupture. Although absolute time was not recorded on the array elements, a relative time base was established using the main shock hypocentral P wave and the P and S waves from a later aftershock. A cross-correlation technique was used to measure the difference in arrival times of individual seismic waves in a moving 0.6 to 1.2 sec window at each array element, which would then be converted into the wave's slowness (1/velocity) along the array. When applied to the main shock vertical and horizontal accelerograms, results from both components of motion indicated that the early arriving energy came from a source to the south of the array, and the source of the energy moved rapidly to the north of the array during the strong shaking. The ground motions at the array elements were well correlated for about the first 11 sec of motion. These observations suggest that we have observed the initiation of rupture south of the array and its subsequent propagation along the fault to a position north of the array in about 10 sec, and that the energy was radiated from a fairly compact region around the rupture front. If the observed vertical and horizontal ground motions are assumed to be caused by P and S waves, respectively, then the observed slownesses show irregularities which can be interpreted as implying that the observed high-frequency ground motions originated at irregularly distributed regions on the fault surface, or that the rupture velocity was variable, or both. One possible interpretation of the data suggests that the rupture proceeded at near P-wave velocity over a 7-km-long section of fault. Average rupture velocities of about 2.7 to 3.2 km/sec at 8 km depth are consistent with the data, and 2.8 km/sec is weakly preferred under the assumption that rupture propagates at a fixed fraction of the shear velocity. The large vertical pulse, which had a peak acceleration of 1.7 g at E06, was emitted from the portion of the fault extending 25 to 30 km northwest of the hypocenter near Meloland overpass, and not from the point on the fault closest to the differential array. Nothing can be said about fault behavior southeast of the hypocenter.

scholarly journals Crustal deformation and fault slip during the seismic cycle in the North Chile subduction zone, from GPS and InSAR observations

2004 ◽  
Vol 158 (2) ◽  
pp. 695-711 ◽  
Author(s):  
M. Chlieh ◽  
J. B. de Chabalier ◽  
J. C. Ruegg ◽  
R. Armijo ◽  
R. Dmowska ◽  
...  
Keyword(s):  
Subduction Zone ◽  
Crustal Deformation ◽  
Fault Slip ◽  
Seismic Cycle ◽  
The North

scholarly journals Spatial–temporal properties of afterslip associated with the 2015 Mw 8.3 Illapel earthquake, Chile

2021 ◽  
Vol 73 (1) ◽  
Author(s):  
Yunfei Xiang ◽  
Jianping Yue ◽  
Zhongshan Jiang ◽  
Yin Xing
Keyword(s):  
Early Stage ◽  
Near Field ◽  
Temporal Distribution ◽  
Slip Rate ◽  
Fault Slip ◽  
Coseismic Slip ◽  
Temporal Properties ◽  
Time Period ◽  
Illapel Earthquake ◽  
Postseismic Slip

AbstractIn order to characterize the spatial–temporal properties of postseismic slip motions associated with the 2015 Illapel earthquake, the daily position time series of 13 GNSS sites situated at the near-field region are utilized. Firstly, a scheme of postseismic signal extraction and modeling is introduced, which can effectively extract the postseismic signal with consideration of background tectonic movement. Based on the extracted postseismic signal, the spatial–temporal distribution of afterslip is inverted under the layered medium model. Compared with coseismic slip distribution, the afterslip is extended to both deep and two sides, and two peak slip patches are formed on the north and south sides. The afterslip is mainly cumulated at the depth of 10–50 km, and the maximum slip reaches 1.46 m, which is situated at latitude of − 30.50°, longitude of − 71.78°, and depth of 18.94 m. Moreover, the postseismic slip during the time period of 0–30 days after this earthquake is the largest, and the maximum of fault slip and corresponding slip rate reaches 0.62 m and 20.6 mm/day. Whereas, the maximum of fault slip rate during the time period of 180–365 days is only around 1 mm/day. The spatial–temporal evolution of postseismic slip motions suggests that large postseismic slip mainly occurs in the early stage after this earthquake, and the fault tend to be stable as time goes on. Meanwhile, the Coulomb stress change demonstrate that the postseismic slip motions after the Illapel earthquake may be triggered by the stress increase in the deep region induced by coseismic rupture.

The kinematics of crustal deformation in Java from GPS observations: Implications for fault slip partitioning

2017 ◽  
Vol 458 ◽  
pp. 69-79 ◽  
Author(s):  
A. Koulali ◽  
S. McClusky ◽  
S. Susilo ◽  
Y. Leonard ◽  
P. Cummins ◽  
...  
Keyword(s):  
Crustal Deformation ◽  
Fault Slip ◽  
Slip Partitioning ◽  
Gps Observations

Mechanical Models Suggest Fault Linkage through the Imperial Valley, California, U.S.A.

2019 ◽  
Vol 109 (4) ◽  
pp. 1217-1234 ◽  
Author(s):  
Jacob H. Dorsett ◽  
Elizabeth H. Madden ◽  
Scott T. Marshall ◽  
Michele L. Cooke
Keyword(s):  
Southern California ◽  
Slip Rate ◽  
Fault Slip ◽  
Surface Strain ◽  
Plate Motion ◽  
Seismic Zone ◽  
Rate Data ◽  
Imperial Valley ◽  
Cerro Prieto

Abstract The Imperial Valley hosts a network of active strike‐slip faults that comprise the southern San Andreas fault (SAF) and San Jacinto fault systems and together accommodate the majority of relative Pacific–North American plate motion in southern California. To understand how these faults partition slip, we model the long‐term mechanics of four alternative fault networks with different degrees of connectivity through the Imperial Valley using faults from the Southern California Earthquake Center Community Fault Model version 5.0 (v.5.0). We evaluate model results against average fault‐slip rates from the Uniform California Earthquake Rupture Model v.3 (UCERF3) and geologic slip‐rate estimates from specific locations. The model results support continuous linkage from the SAF through the Brawley seismic zone to the Imperial and to the Cerro Prieto faults. Connected faults decrease surface strain rates throughout the region and match more slip‐rate data. Only one model reproduces the UCERF3 rate on the Imperial fault, reaching the lower bound of 15  mm/yr. None of the tested models reproduces the UCERF3 preferred rate of 35  mm/yr. In addition, high‐strain energy density rates around the Cerro Prieto fault in all models suggest that the UCERF3 preferred rate of 35  mm/yr may require revision. The Elmore Ranch fault‐slip rate matches the UCERF3 rate only in models with continuous linkage. No long‐term slip‐rate data are available for the El Centro and Dixieland faults, but all models return less than 2  mm/yr on the El Centro fault and 3.5–9.6  mm/yr on the Dixieland fault. This suggests that the Dixieland fault may accommodate a significant portion of plate‐boundary motion.

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