On the variation of seismic hazard along the San Andreas fault

1984 ◽  
Vol 74 (2) ◽  
pp. 709-723
Author(s):  
B. F. Howell
Keyword(s):  
Seismic Hazard ◽  
San Francisco ◽  
San Andreas Fault ◽  
The Other ◽  
Plain Area ◽  
San Andreas ◽  
Focal Area ◽  
Large Ratio ◽  
Earthquake Size

Abstract Recurrence probabilities of earthquakes were evaluated at 33 locations along the San Andreas fault using Gumbel's method. Two minima in the mode of the largest annual earthquakes occur, one north of San Francisco centered around 38.75°N latitude and the other centered in the Carizzo Plain area at 35.25°N latitude. The latter is offset by an unusually large ratio of large to small earthquakes, so that only one minimum (around 38.75°N) is observed in the expected 100-yr earthquake size. This broad minimum closely coincides with where the San Andreas fault broke in 1906, and may be only temporary. There appears to be a slight, systematic tendency for the observed largest 50-year earthquake to become larger than the expected 50-yr earthquake as the size of the area being studied is reduced. The preferred explanation for this is that the pattern of size as a function of frequency becomes nonlinear when the size of the area studied is less than the focal area of the largest earthquakes.

PALEOSEISMIC EXCAVATIONS ACROSS THE SAN ANDREAS FAULT ON THE SAN FRANCISCO PENINSULA, WOODSIDE, CALIFORNIA

2018 ◽  
Author(s):  
Carol S. Prentice ◽  
◽  
Robert R. Sickler ◽  
Kevin B. Clahan ◽  
Alexandra Pickering ◽  
...  
Keyword(s):  
San Francisco ◽  
San Andreas Fault ◽  
San Andreas

Crustal structure southwest of the San Andreas fault from quarry blasts

1964 ◽  
Vol 54 (1) ◽  
pp. 67-77
Author(s):  
Robert M. Hamilton ◽  
Alan Ryall ◽  
Eduard Berg
Keyword(s):  
San Francisco ◽  
Crustal Structure ◽  
San Andreas Fault ◽  
P Wave ◽  
Geological Survey ◽  
San Andreas ◽  
Crustal Model ◽  
Crystalline Crust ◽  
The U.S

abstract To determine a crustal model for the southwest side of the San Andreas fault, six large quarry blasts near Salinas, California, were recorded at 27 seismographic stations in the region around Salinas, and along a line northwest of the quarry toward San Francisco. Data from these explosions are compared with results of explosion-seismic studies carried out by the U.S. Geological Survey on a profile along the coast of California from San Francisco to Camp Roberts. The velocity of Pg, the P wave refracted through the crystalline crust, in the Salinas region is 6.2 km/sec and the velocity of Pn is about 8.0 km/sec. Velocities of the direct P wave in near-sur-face rocks vary from one place to another, and appear to correlate well with gross geologic features. The thickness of the crust in the region southwest of the San Andreas fault from Salinas to San Francisco is about 22 kilometers.

Quantitative Refinement of Calibrated14C Distributions

1994 ◽  
Vol 41 (1) ◽  
pp. 1-18 ◽  
Author(s):  
Glenn P. Biasi ◽  
Ray Weldon
Keyword(s):  
Sedimentation Rate ◽  
Quantitative Data ◽  
San Andreas Fault ◽  
Bayes Theorem ◽  
The Other ◽  
Historical Information ◽  
Extra Information ◽  
San Andreas ◽  
Mean And Variance ◽  
The Bayesian Approach

AbstractA new method is presented for using known ordering or other relationships between14C samples to reduce14C dating uncertainty. The order of sample formation is often known from, for example, stratigraphic superposition, dendrochronology, or crosscutting field relations. Constraints such as a minimum time between dates and limits from historical information are also readily included. Dendrochronologically calibrated calendric date histograms initially represent each date. The method uses Bayes theorem and the relational constraints to upweight date ranges in each date distribution consistent with the other date distributions and the constraints, and downweight unlikely portions. The reweighted date distributions retain all dating possibilities present in the initial calibrated date distributions, but each date in the result now reflects the extra information such as ordering supplied through the constraints. In addition, one may add information incrementally, and thus analyze systematically its effect on all the date distributions. Thus, the method can be used to assess the consistency of the quantitative data at hand. The Bayesian approach also uses the empirical calibrated date distributions directly, so information is not lost prematurely by summarized dates to a mean and variance or "confidence intervals." The approach is illustrated with data from two densely sampled paleoseismic sites on the San Andreas Fault in southern California. An average reduction in14C date distribution variance of 59% is achieved using ordering information alone, and 85% is achieved by also applying sedimentation rate constraints and historical information.

scholarly journals Fractal properties and simulation of micro-seismicity for seismic hazard analysis: a comparison of North Anatolian and San Andreas Fault Zones

2012 ◽  
Vol 2 (1) ◽  
pp. 1 ◽  
Author(s):  
Naside Ozer ◽  
Savas Ceylan
Keyword(s):  
Fractal Dimension ◽  
Seismic Hazard ◽  
Fault Zone ◽  
San Andreas Fault ◽  
Fractal Dimensions ◽  
Fault Zones ◽  
Group Method ◽  
Western Anatolia ◽  
P Value ◽  
San Andreas

We analyzed statistical properties of earthquakes in western Anatolia as well as the North Anatolian Fault Zone (NAFZ) in terms of spatio-temporal variations of fractal dimensions, p- and b-values. During statistically homogeneous periods characterized by closer fractal dimension values, we propose that occurrence of relatively larger shocks (M >= 5.0) is unlikely. Decreases in seismic activity in such intervals result in spatial b-value distributions that are primarily stable. Fractal dimensions decrease with time in proportion to increasing seismicity. Conversely, no spatiotemporal patterns were observed for p-value changes. In order to evaluate failure probabilities and simulate earthquake occurrence in the western NAFZ, we applied a modified version of the renormalization group method. Assuming an increase in small earthquakes is indicative of larger shocks, we apply the mentioned model to micro-seismic (M<= 3.0) activity, and test our results using San Andreas Fault Zone (SAFZ) data. We propose that fractal dimension is a direct indicator of material heterogeneity and strength. Results from a model suggest simulated and observed earthquake occurrences are coherent, and may be used for seismic hazard estimation on creeping strike-slip fault zones.

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