Our rupture models are characterized by spatially … PARKFIELD EARTHQUAKE JUNE 27, 1966 Time (s) 10Fig. It is found that (1) Mb = 5.8 and M~ = 6.4 as compared to Mb = 5.4 and Ms = 5.4 for the foreshock (04:08:54), (2) both the Rayleigh and Love wave radiation patterns conform to those of a double couple at a depth of about 8.6 km, (3) the main shock … One interpretation of the fresh cracks and broken pipeline is that a few centimeters or more of slip occurred on the fault zone just before the 1966 shock. It is found that (1) Mb = 5.8 and Ms = … The earthquakes that occurred on the Parkfield section of the San Andreas fault in 1857, 1881, 1901, 1922, 1934, and 1966 provide a wealth of information. The 1966 Parkfield earthquake (M6) marked in some ways the beginning of the modern era of seismology in California. Bakun and McEvilly (1997, 1984) compared seismograms from the 1922, 1934 and 1966 Parkfield earthquakes as part of the evidence supporting the hypothesis that these events are members of a sequence of characteristic earthquakes. It has been suggested that the 1983 Coalinga earthquake (magnitude 6.4, located outside of the clickable map area), 40 km northeast of Parkfield, could have altered the stress of the San Andreas fault enough at Parkfield to throw off the timing of the next magnitude 6 shock, or maybe "defuse" it somewhat, causing less energy to be released at Parkfield. Most tests of earthquake size and interval distributions at Parkfield treat the region in isolation, ignoring the process by which Parkfield was identified from the earthquake record used to test the hypotheses. In all respects, the "17-minute" foreshocks in 1934 and in 1966 were essentially identical. Citing articles via. TIME: June 27, 1966 / 9:26 pm PDT The surface-wave magnitude for the 1966 main shock is 6.0. Open in new tab Download slide (a) A map of the Parkfield … MAGNITUDE: ML6.0 He is also the Co-Director of the Southern California Earthquake Center.. The 1966 sequence occurred in an area where measured deformation across the fault for 1959-1965 shows a decrease from about 2 cm/year to the north to zero to the south of the area. GHC is within 0.5 km of the zone of ground breakage associated with the earthquake. The model succeeds in reproducing a realistic earthquake sequence of irregular moment magnitude (M w) 6.0 main shocks—including events similar to the ones in 1966 and 2004—and provides an excellent match for the detailed interseismic, coseismic, and postseismic observations collected along this fault during the most recent earthquake cycle. As in 1934, there is a discrepancy in the ML estimates obtained from northern (ML = 5.5) and southern (ML = 5.8) California seismographs. How similar were the 1934 and 1966 Parkfield earthquakes? Figure 1 . The Parkfield bridge, built in 1932, was damaged in 1934, and 1966 Parkfield earthquakes. In the present section, the main shock of the Parkfield 1966 earthquake is analysed by interpreting the recorded strong ground motion recordings using standard seismological theory on seismic waves; ray arguments are supplied to infer the rupture velocity during this earthquake. In all respects, the "17-minute" foreshocks in 1934 and in 1966 were essentially identical. In April 1985, the USGS issued a prediction that an earthquake of approximately magnitude 6 would occur before 1993 on the San Andreas fault near Parkfield, which gained this little town of 34 inhabitants national fame as being the site of the first officially recognized scientific prediction of an earthquake in the United States. As in 1934, a magnitude 5 Parkfield foreshock occurred 17 minutes before the main shock on June 28, 1966. The connection of these events to the characteristic earthquakes at Parkfield is suggested by the fact that waveforms from the November, 1993 event were identical to those from a foreshock three days before the 1966 Parkfield mainshock. By J. Archuleta, Steven and M. Day. LENGTH OF RUPTURE: about 27 km (17 miles) FIG. The most recent significant earthquake to occur here happened on September 28, 2004. In conclusion, examination of geodetic data from the 1966 and 1934 earthquake indicate that the 196 event actually propagated south of Gold Hill. Since 1966, there has been no earthquake greater than 5.0 at Parkfield. 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. PARKFIELD EARTHQUAKES OF JUNE 27-29, 1966, MONTEREY AND SAN LUIS OBISPO COUNTIES, CALIFORNIA-- PRELI~IINARY REPORT ABSTRACT Two earthquakes, M = 5.3 and 5.5, shook the Parkfield area in southern Monterey County, California, at 0409:56.5 and 0426:13.8 GMT, 28 June 1966. However, none of the earthquakes in Table 1 appears to be a repeat of the "17-minute" foreshocks. Since 1966, there has been no earthquake greater than 5.0 at Parkfield. The Parkfield earthquake of June 28, 1966 (04:26:12.4 GMT)is studied using short-period and long-period teleseismic records. (a) Best model (model that best fits the data). Rupture model for the 1966 Parkfield earthquake: slip amplitude (color scale) and rupture time (white lines are 1‐s contours). The results of this comparison provide a test ofthe potential for an M=6 earthquake in the Parkfield area by 1988, a test that is independent of the periodicity, oraperiodicity, oftheearth-quake sequence before 1966. Hypothesis Moderate-size earthquakes of about magnitude 6 have occurred on the Parkfield section of the San Andreas fault at fairly regular intervals - in 1857, 1881, 1901, 1922, 1934, and 1966. The red star marks the 1966 hypocenter. The 1966 M6 Parkfield earthquake (and presumably several previous M6 events in the area) nucleated under Middle Mountain (MM) and propagated along the SAF towards the SE, while the 2004 M6 Parkfield earthquake started near Gold Hill (GH) and propagated primarily in the opposite direction (Bakun et al. This event was one of the largest to occur in central California since 1906. What is more significant about the 1966 Parkfield earthquake is that the USGS used it to suggest a 21-to-22-year periodicity of magnitude 6 earthquakes at Parkfield. The Parkfield earthquake of June 28, 1966 (04:26:12.4 GMT) is studied using short-period and long-period teleseismic records. LOCATION: 35° 56' N, 120° 31' W 10 km (6 miles) NW of the the town of Parkfield In fact, landslides and nontectonic surface cracks were observed northwest of Middle Mountain at the time of the 1966 Parkfield earthquake. The earlier Parkfield earthquakes were similar to the 1966 event, leading to the hypothesis of a characteristic Parkfield earthquake with recurring, recognizable source features. Because no surface break occurred during either earthquake (1966 and 2004), the fault plane is buried 500 m below the surface. about 9 hours before the 1966 main shock. As an example of this method, a simulation of the 1966 Parkfield, California earthquake is made. 5 Ground displacement, perpendicular to the fault strike, about 10 km south-east and 3 km … 2005). As in 1934, rupture during the main shock began on Middle Mountain and propagated southeastward along the fault to near the offset in the fault trace southeast of Gold Hill. FAULT RUPTURED: San Andreas fault 2 (a) Map of Parkfield area showing location of the earthquakes of magnitude 2 and greater for the period 28 January 1966 thru 30 June 1966 (McEvilly et … Because the surface waves generated by the 1934 main shock are nearly identical to those generated in 1922 and in 1966, the surface-wave magnitudes for the 1922, 1934 and 1966 main shocks are all about 6. Gregory C. Beroza (born October 10, 1959) is a seismologist and professor of geophysics at Stanford University. Component: 355 PGA (cm/s/s):-347.82 PGV (cm/s):-23.17 Add this to bin: Component: 85 PGA (cm/s/s):-425.68 PGV (cm/s):-25.44 Add this to bin: Component: Down PGA (cm/s/s):-116.89 PGV (cm/s): 7.28 Add this to bin TO THE 1966 PARKFIELD EARTHQUAKE BY STEWART W. SMITH AND MAX WYss ABSTRACT Immediately following the 1966 Parkfield earthquake a continuing program of fault displacement measurements was undertaken, and several types of instru- ments were installed in the fault zone to monitor ground motion. Susana Custodio, & Ralph J. Archuleta Published May 2007, SCEC Contribution #1008 We model the two most recent M w ∼6 Parkfield, California, earthquakes, which occurred in 1966 and 2004, from a nonlinear global inversion of near-fault strong motion seismograms. For a more detailed look at the Parkfield Earthquake Prediction Experiment, see Volume 20, Number 2, of Earthquakes and Volcanoes, 1988. Here we propose an alternative, or "null" hypothesis: that magnitude distribution throughout California obeys a Guten- berg-Richter (GR) law modified at the high … MAXIMUM SURFACE OFFSET: about 10 cm (4 inches). CrossRef. The arrow points out the 10-cm (4-inch) right-lateral offset in the dividing stripe. 98, 4527–4538 (1993) ADS Article Google Scholar 19. Such … J. Geophys. This landlside occured in the mid 1990's and was nontectonic in orgin. The year 1993 came and went with no magnitude 6 earthquakes in the area, though Parkfield did experience a magnitude 4.7 quake on October 20, 1992, a magnitude 4.4 on April 4, 1993, a magnitude 5.0 on November 14, 1993, and a magnitude 4.9 on December 20, 1994. Dynamic rupture in a layered medium: the 1966 Parkfield earthquake . Tsai, Y.-B. The negative result … It is found that (1) M b = 5.8 and M s = 6.4 as compared to M b = 5.4 and M s = 5.4 for the foreshock (04:08:54), (2) both the Rayleigh and Love wave radiation patterns conform to those of a double couple at a depth of about 8.6 km, (3) the main shock … POWERED BY . 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