Seismic Evidence for Rock Damage and Healing on the San Andreas Fault Associated with the 2004 M 6.0 Parkfield Earthquake

2006 ◽  
Vol 96 (4B) ◽  
pp. S349-S363 ◽  
Author(s):  
Y.-G. Li
Keyword(s):  
San Andreas Fault ◽  
Rock Damage ◽  
San Andreas ◽  
Parkfield Earthquake

Localization of seismicity prior to large earthquakes

2021 ◽  
Author(s):  
Ilya Zaliapin ◽  
Yehuda Ben-Zion
Keyword(s):  
Laboratory Experiments ◽  
San Andreas Fault ◽  
Rock Damage ◽  
San Andreas ◽  
Aftershock Sequences ◽  
Background Seismicity ◽  
Seismogenic Faults ◽  
Parkfield Earthquake ◽  
Background Events ◽  
Large Earthquakes

<p>We present results aimed at understanding preparation processes of large earthquakes by tracking progressive localization of earthquake deformation with three complementary analyses: (i) estimated production of rock damage by background events, (ii) spatial localization of background seismicity within damaged areas, and (iii) progressive coalescence of individual earthquakes into clusters. Techniques (i) and (ii) employ declustered catalogs to avoid the occasional strong fluctuations associated with aftershock sequences, while technique (iii) examines developing clusters in entire catalog data. The different techniques provide information on different time scales and on the spatial extent of weakened damaged regions. The analyses reveal generation of earthquake-induced rock damage on a decadal timescale around eventual rupture zones, and progressive localization of background seismicity on a 2-3 yr timescale before several M > 7 earthquakes in southern and Baja California and M7.9 events in Alaska. This is followed by coalescence of earthquakes into growing clusters that precede the mainshocks. Corresponding analysis around the 2004 M6 Parkfield earthquake in the creeping section of the San Andreas fault shows contrasting tendencies to those associated with the large seismogenic faults. The results are consistent with observations from laboratory experiments and physics-based models with heterogeneous materials not dominated by a pre-existing failure zone. Continuing studies with these techniques, combined with analysis of geodetic data and insights from laboratory experiments and model simulations, may allow developing an integrated multi-signal procedure to estimate the approaching time and size of large earthquakes.</p>

Control of rupture by fault geometry during the 1966 parkfield earthquake

1981 ◽  
Vol 71 (1) ◽  
pp. 95-116 ◽  
Author(s):  
Allan G. Lindh ◽  
David M. Boore
Keyword(s):  
Main Shock ◽  
Fault Plane ◽  
San Andreas Fault ◽  
Strong Motion ◽  
P Wave ◽  
Fault Geometry ◽  
Dynamic Rupture ◽  
San Andreas ◽  
Hill Station ◽  
Parkfield Earthquake

abstract A reanalysis of the available data for the 1966 Parkfield, California, earthquake (ML=512) suggests that although the ground breakage and aftershocks extended about 40 km along the San Andreas Fault, the initial dynamic rupture was only 20 to 25 km in length. The foreshocks and the point of initiation of the main event locate at a small bend in the mapped trace of the fault. Detailed analysis of the P-wave first motions from these events at the Gold Hill station, 20 km southeast, indicates that the bend in the fault extends to depth and apparently represents a physical discontinuity on the fault plane. Other evidence suggests that this discontinuity plays an important part in the recurrence of similar magnitude 5 to 6 earthquakes at Parkfield. Analysis of the strong-motion records suggests that the rupture stopped at another discontinuity in the fault plane, an en-echelon offset near Gold Hill that lies at the boundary on the San Andreas Fault between the zone of aseismic slip and the locked zone on which the great 1857 earthquake occurred. Foreshocks to the 1857 earthquake occurred in this area (Sieh, 1978), and the epicenter of the main shock may have coincided with the offset zone. If it did, a detailed study of the geological and geophysical character of the region might be rewarding in terms of understanding how and why great earthquakes initiate where they do.

scholarly journals Displacement on the San Andreas fault subsequent to the 1966 Parkfield earthquake

1968 ◽  
Vol 58 (6) ◽  
pp. 1955-1973
Author(s):  
Stewart W. Smith ◽  
Max Wyss
Keyword(s):  
Shear Stress ◽  
Ground Motion ◽  
San Andreas Fault ◽  
High Rate ◽  
Aftershock Activity ◽  
Fault Surface ◽  
San Andreas ◽  
Parkfield Earthquake ◽  
Fault Displacement ◽  
Displacement Measurements

ABSTRACT Immediately following the 1966 Parkfield earthquake a continuing program of fault displacement measurements was undertaken, and several types of instruments were installed in the fault zone to monitor ground motion. In the year subsequent to the earthquake a maximum of at least 20 cm of displacement occurred on a 30 km section of the San Andreas fault, which far exceeded the surficial displacement at the time of the earthquake. The rate of displacement decreased logarithmically during this period in a manner similar to that of the decrease in aftershock activity. After the initial high rate of activity it could be seen that most of the displacement was occurring in 4–6 day epochs of rapid creep following local aftershocks. The variation of fault displacement along the surface trace was measured and shown to be consistent with a vertidal fault surface 44 km long and 14 km deep, along which a shear stress of 2.4 bars was relieved.

scholarly journals Seismicity alert probabilities at Parkfield, California, revisited

1998 ◽  
Vol 88 (1) ◽  
pp. 117-130
Author(s):  
Andrew J. Michael ◽  
Lucile M. Jones
Keyword(s):  
Uniform Distribution ◽  
Earthquake Prediction ◽  
Confidence Level ◽  
San Andreas Fault ◽  
Strike Slip ◽  
San Andreas ◽  
Background Seismicity ◽  
Parkfield Earthquake ◽  
The U.S

Abstract For a decade, the U.S. Geological Survey has used the Parkfield Earthquake Prediction Experiment scenario document to estimate the probability that earthquakes observed on the San Andreas fault near Parkfield will turn out to be foreshocks followed by the expected magnitude 6 mainshocks. During this time, we have learned much about the seismogenic process at Parkfield, about the long-term probability of the Parkfield mainshock, and about the estimation of these types of probabilities. The probabilities for potential foreshocks at Parkfield are reexamined and revised in light of these advances. As part of this process, we have confirmed both the rate of foreshocks before strike-slip earthquakes in the San Andreas physiographic province and the uniform distribution of foreshocks with magnitude proposed by earlier studies. Compared to the earlier assessment, these new estimates of the long-term probability of the Parkfield mainshock are lower, our estimate of the rate of background seismicity is higher, and we find that the assumption that foreshocks at Parkfield occur in a unique way is not statistically significant at the 95% confidence level. While the exact numbers vary depending on the assumptions that are made, the new alert probabilities are lower than previously estimated. Considering the various assumptions and the statistical uncertainties in the input parameters, we also compute a plausible range for the probabilities. The range is large, partly due to the extra knowledge that exists for the Parkfield segment, making us question the usefulness of these numbers.

Accumulation of tectonic strain in California

1970 ◽  
Vol 60 (6) ◽  
pp. 1877-1896
Author(s):  
J. C. Savage ◽  
R. O. Burford
Keyword(s):  
Shear Strain ◽  
San Andreas Fault ◽  
Geodetic Survey ◽  
Strain Accumulation ◽  
Owens Valley ◽  
Imperial Valley ◽  
San Andreas ◽  
Period 1880 ◽  
Tectonically Active ◽  
Parkfield Earthquake

Abstract The shear-strain accumulation in five tectonically-active areas of California has been calculated from triangulation data supplied by the U. S. Coast and Geodetic Survey. Three of the areas lie along active sections of the San Andreas fault. Near Hollister, no appreciable strain accumulation was detected for the period 1930 to 1962. The movement of the fault blocks there appears to be accommodated by slip on the San Andreas and Calaveras faults. Near Cholame, the only appreciable accumulation of shear strain in the period 1932 to 1962 appears to be associated directly with slip on the San Andreas north of Cholame, slip which probably occurred during the 1934 Parkfield earthquake. Significant strain accumulation was confined to a zone centered on the San Andreas fault and extending 10 km on either side. Some of this strain was released in the 1966 Parkfield earthquake. In Imperial Valley, an average accumulation of γ = 0.4 μstrain per year right-lateral (referred to vertical planes parallel to the Imperial fault) shear strain extends over a zone perhaps 100 km wide centered on the Imperial fault. It appears that this shear pattern may be resolved into two zones of shear, one concentrated near the Imperial fault and the other near the San Andreas fault. No appreciable shear-strain accumulation was detected in the two areas that do not lie on the San Andreas fault—Santa Barbara channel for the period 1880 to 1923 and Owens Valley for the period 1934 to 1956.

Accelerograms—Parkfield earthquake

1967 ◽  
Vol 57 (6) ◽  
pp. 1179-1192 ◽  
Author(s):  
William K. Cloud ◽  
Virgilio Perez
Keyword(s):  
Short Duration ◽  
Main Shock ◽  
San Andreas Fault ◽  
Response Spectra ◽  
Acceleration Pulse ◽  
San Andreas ◽  
High Acceleration ◽  
Earthquake Series ◽  
Parkfield Earthquake ◽  
Electric Analog

Abstract Five accelerograms obtained during the main shock of the Parkfield earthquake series at locations adjacent to and within 10 miles of the trace of the San Andreas fault are presented together with limited analysis by electric analog methods. With one exception records from horizontal accelerometers are characterized by a short duration section of high acceleration. Adjacent to faulting an acceleration pulse of 0.5 gravity was recorded. Judged by a record from a station east of the fault on rock and a record from a station approximately the same distance west of the fault on alluvium, magnification of response spectra by alluvium was less than a factor of 3.

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