Do historical rates of seismicity in southern California require the occurrence of earthquake magnitudes greater than would be predicted from fault length?

1997 ◽  
Vol 87 (6) ◽  
pp. 1662-1666 ◽  
Author(s):  
Mark W. Stirling ◽  
Steven G. Wesnousky
Keyword(s):  
Working Group ◽  
Southern California ◽  
Active Faults ◽  
Historical Seismicity ◽  
Historical Distribution ◽  
Large Earthquakes ◽  
Fault Length

Abstract The Working Group on California Earthquake Probabilities reported a discrepancy between the historical rates of large earthquakes in southern California and rates predicted from interpretation of geological, geodetic, and historical seismicity data. It was suggested that the discrepancy may be due to the assumption within their analysis that the magnitude of the largest earthquake on a fault is limited by the mapped fault length. Our analysis of the available data does not support the presence of a historical deficit in the rate of seismicity, nor does it require that earthquakes that rupture beyond the lengths of mapped active faults in southern California, or that rupture numerous subparallel faults, are needed to explain the historical distribution of seismicity.

Interactions of Earthquakes in Central Italy over the Past 100 Yr through Coulomb Stress Changes, and Implications for Seismic Hazards

2020 ◽  
Vol 110 (1) ◽  
pp. 178-190 ◽  
Author(s):  
Bin Shan ◽  
Yashan Feng ◽  
Chengli Liu ◽  
Xiong Xiong
Keyword(s):  
Central Italy ◽  
Active Faults ◽  
Earthquake Hazard ◽  
Seismic Hazards ◽  
Historical Seismicity ◽  
Normal Faults ◽  
Coulomb Stress Changes ◽  
Earthquake Hazard Assessment ◽  
Stress Changes ◽  
Large Earthquakes

ABSTRACT Italy has a historical earthquake record that is complete for events with a magnitude above 5.8 since A.D. 1349, making it possible to study Coulomb failure stress changes (ΔCFS) over a long period. In this study, we investigated the interactions between moderate-to-large earthquakes through ΔCFS over 100 yr in central Italy. This region is characterized by intense seismicity with predominantly extensional components. Hence, earthquake hazard assessment is of great public concern. Besides, earthquake interactions on normal faults are relatively less studied compared to reverse and strike-slip faults. ΔCFS calculations in this study incorporated both coseismic stress transfer and postseismic viscoelastic relaxation, and found the epicenters of 13 out of 15 events located in positively stressed lobes induced by previous earthquakes, confirming a correlation between the ΔCFS pattern and locations of moderate-to-large earthquakes. Next, we estimated the current distribution of ΔCFS on active faults, and after a comprehensive analysis of ΔCFS accumulation, slip rates, historical seismicity, and locations of populated cities, we identified three regions of potential seismic hazards in this region.

scholarly journals The recent instrumental seismicity of Syria and its implications

2018 ◽  
Vol 57 (2) ◽  
Author(s):  
Mohamad Khir Abdul-Wahed ◽  
Jamal Asfahani
Keyword(s):  
Seismic Activity ◽  
Current Knowledge ◽  
Active Faults ◽  
Historical Seismicity ◽  
Focal Mechanisms ◽  
Seismic Events ◽  
Earthquake Activity ◽  
Return Periods ◽  
Cluster Type ◽  
Large Earthquakes

This contribution is an attempt to enlarge the current knowledge about the recent instrumental seismicity, recorded during the period 1995- 2012 by the Syrian national seismological network, as well as the seismotectonic settings in Syria. The recent instrumental seismicity has shown that the earthquake activity has produced a little number of low magnitude events. Consequently, it indicates that this activity is actually passing through a relative quiescence in comparison with the historical seismicity. The correlation between the instrumental seismicity and the seismotectonic features was performed by analyzing spatial distributions of seismic events and focal mechanisms of some strongest events. The current results, allow observing many types of the seismic activity as follows: Swarm-type, Cluster- type, and Occasional-type, which could improve the understanding of the behavior of the seismically active faults. The long return periods of large earthquakes (M?5) and the shortness of instrumental seismicity, prevent us to completely characterize the seismic activity and to discover all the active faults in the country.

scholarly journals A decade of progress in seismology since the Edgecumbe earthquake

1997 ◽  
Vol 30 (2) ◽  
pp. 163-166
Author(s):  
Euan G. C. Smith
Keyword(s):  
New Zealand ◽  
Site Response ◽  
Active Faults ◽  
Strong Motion ◽  
Historical Seismicity ◽  
Ground Acceleration ◽  
Earthquake Catalogues ◽  
Motion Data ◽  
Moderate Earthquake ◽  
Large Earthquakes

During the decade, the contemporaneous increase in data from moderately large earthquakes in New Zealand (and overseas) and the re-equipping of the New Zealand seismograph and accelerograph networks has seen good progress on several fronts. Earthquakes are now more accurately located and their spatial distribution is better defined. There have been improvements in the various databases used for seismic hazard assessments: active faults, earthquake catalogues, historical seismicity, and strong ground motions. The increase in strong-motion data has enabled the development of better models for Peak Ground Acceleration, and the effect of site conditions on site response, particularly for weak-to-moderate earthquake motions, has been studied in detail.

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.

CRUSTAL DEFORMATION STUDIES IN JAVA (INDONESIA) USING GPS

2009 ◽  
Vol 03 (02) ◽  
pp. 77-88 ◽  
Author(s):  
HASANUDDIN Z. ABIDIN ◽  
HERI ANDREAS ◽  
TERUYUKI KATO ◽  
TAKEO ITO ◽  
IRWAN MEILANO ◽  
...  
Keyword(s):  
Active Faults ◽  
Fault Zones ◽  
First Year ◽  
Horizontal Deformation ◽  
West Java ◽  
Plate Movement ◽  
Tsunami Earthquake ◽  
Second Year ◽  
Seismic Deformation ◽  
Large Earthquakes

Along the Java trench the Australian–Oceanic plate is moving and pushing onto and subducting beneath the Java continental crust at a relative motion of about 70 mm/yr in NNE direction. This subduction-zone process imposed tectonic stresses on the fore-arc region offshore and on the land of Java, thus causing the formation of earthquake fault zones to accommodate the plate movement. Historically, several large earthquakes happened in Java, including West Java. This research use GPS surveys method to study the inter-seismic deformation of three active faults in West Java region (i.e. Cimandiri, Lembang and Baribis faults), and the co-seismic and post-seismic deformation related to the May 2006 Yogyakarta and the July 2006 South Java earthquakes. Based on GPS surveys results it was found that the area around Cimandiri, Lembang and Baribis fault zones have the horizontal displacements of about 1 to 2 cm/yr or less. Further research is however still needed to extract the real inter-seismic deformation of the faults from those GPS-derived displacements. GPS surveys have also estimated that the May 2006 Yogyakarta earthquake was caused by the sinistral movement of the (Opak) fault with horizontal co-seismic deformation that generally was less than 10 cm. The post-seismic horizontal deformation of the July 2006 South Java tsunami earthquake has also been estimated using GPS surveys data. In the first year after the earthquake (2006 to 2007), the post-seismic deformation is generally less than 5 cm; and it becomes generally less than 3 cm in the second year (2007 to 2008).

A multidisciplinary approach to seismic hazard in southern California

1994 ◽  
Vol 84 (5) ◽  
pp. 1293-1309
Author(s):  
Steven N. Ward
Keyword(s):  
Seismic Hazard ◽  
Southern California ◽  
Current Model ◽  
Seismic Hazard Assessment ◽  
Historical Seismicity ◽  
San Andreas ◽  
The Pacific ◽  
Moderate Earthquake ◽  
Earthquake Potential ◽  
Seismic Moment Release

Abstract A serious obstacle facing seismic hazard assessment in southern California has been the characterization of earthquake potential in areas far from known major faults where historical seismicity and paleoseismic data are sparse. This article attempts to fill the voids in earthquake statistics by generating “master model” maps of seismic hazard that blend information from geology, paleoseismology, space geodesy, observational seismology, and synthetic seismicity. The current model suggests that about 40% of the seismic moment release in southern California could occur in widely scattered areas away from the principal faults. As a result, over a 30-yr period, nearly all of the region from the Pacific Ocean to 50 km east of the San Andreas Fault has a greater than 50/50 chance of experiencing moderate shaking of 0.1 g or greater, and about a 1 in 20 chance of suffering levels exceeding 0.3 g. For most of the residents of southern California, thelion's share of hazard from moderate earthquake shaking over a 30-yr period derives from smaller, closer, more frequent earthquakes in the magnitude range (5 ≦ M ≦ 7) rather than from large San Andreas ruptures, whatever their likelihood.

scholarly journals Tectonic Geomorphology and Paleoseismology of the Sharkhai fault: a new source of seismic hazard for Ulaanbaatar (Mongolia)

2021 ◽  
Author(s):  
Abeer Al-Ashkar ◽  
Antoine Schlupp ◽  
Matthieu Ferry ◽  
Ulziibat Munkhuu
Keyword(s):  
Seismic Hazard ◽  
Scaling Laws ◽  
Active Faults ◽  
Seismic Hazard Assessment ◽  
Capital City ◽  
Tectonic Geomorphology ◽  
Time Interval ◽  
Coseismic Slip ◽  
Slip Rates ◽  
Large Earthquakes

Abstract. We present new constraints from tectonic geomorphology and paleoseismology along the newly discovered Sharkhai fault near the capital city of Mongolia. Detailed observations from high resolution Pleiades satellite images and field investigations allowed us to map the fault in detail, describe its geometry and segmentation, characterize its kinematics, and document its recent activity and seismic behavior (cumulative displacements and paleoseismicity). The Sharkhai fault displays a surface length of ~40 km with a slightly arcuate geometry, and a strike ranging from N42° E to N72° E. It affects numerous drainages that show left-lateral cumulative displacements reaching 57 m. Paleoseismic investigations document the faulting and deposition record for the last ~3000 yr and reveal that the penultimate earthquake (PE) occurred between 1515 ± 90 BC and 945 ± 110 BC and the most recent event (MRE) occurred after 860 ± 85 AD. The resulting time interval of 2080 ± 470 years is the first constraint on the Sharkhai fault for large earthquakes. On the basis of our mapping of the surface rupture and the resulting segmentation analysis, we propose two possible scenarios for large earthquakes with likely magnitudes between 6.4 ± 0.2 and 7.1 ± 0.2. Furthermore, we apply scaling laws to infer coseismic slip values and derive preliminary estimates of long-term slip rates between 0.2 ± 0.2 and 1.0 ± 0.5 mm/y. Finally, we propose that these original observations and results from a newly discovered fault should be taken into account for the seismic hazard assessment for the city of Ulaanbaatar and help build a comprehensive model of active faults in that region.

The 1258 Earthquake in Onteniente (Southeast Spain) Not Reported until 2002 in Any Catalog

2020 ◽  
Vol 91 (4) ◽  
pp. 2390-2394
Author(s):  
Elisa Buforn ◽  
Agustín Udías
Keyword(s):  
Iberian Peninsula ◽  
Historical Seismicity ◽  
James I ◽  
Southeast Region ◽  
Tax Exemptions ◽  
The People ◽  
King James I ◽  
The Town ◽  
Large Earthquakes ◽  
Southeast Spain

Abstract Historical seismicity is particularly important for the southeast region of the Iberian Peninsula, where large earthquakes are separated by long periods of time. The study of medieval earthquakes presents special difficulties. In this study, we review the earthquake of 1258 in the town of Onteniente, an event that was not present in regional catalogs of the Iberian Peninsula until 2002. Information about the earthquake is based on a contemporary letter by King James I of Aragon, who granted tax exemptions to the people of the town of Onteniente because of the damage.

Discovery of Ulaanbaatar Fault: A New Earthquake Threat to the Capital of Mongolia

2020 ◽  
Vol 92 (1) ◽  
pp. 437-447
Author(s):  
Yasuhiro Suzuki ◽  
Takashi Nakata ◽  
Mitsuhisa Watanabe ◽  
Sukhee Battulga ◽  
Dangaa Enkhtaivan ◽  
...  
Keyword(s):  
Active Fault ◽  
Active Faults ◽  
Plate Boundaries ◽  
Safety Measures ◽  
Fault Trace ◽  
Seismic Hazard Map ◽  
Fault Scarps ◽  
Japan Aerospace Exploration Agency ◽  
Scope Interpretation ◽  
Large Earthquakes

Abstract Destructive large earthquakes occur not only along major plate boundaries but also within the interior of plates. To establish appropriate safety measures, identifying intraplate active faults and the potential magnitude of associated earthquakes is essential before an earthquake occurs. This study was conducted to document the geomorphic expression of a previously unrecognized 50-km-long active fault in Ulaanbaatar, the capital of Mongolia. Mapping of the fault was accomplished using the Advanced Land Observation Satellite elevation dataset provided by Japan Aerospace Exploration Agency (JAXA), a stereo-scope interpretation of CORONA satellite images, the emplacement of trenches across the fault trace, and field study. The Ulaanbaatar fault (UBF) is marked by fault scarps on the surface and left-lateral stream deflections. The fault displaces late Pleistocene deposits and is thus considered to be active. Based on the length of the fault, the UBF is believed to be capable of causing earthquakes with magnitudes greater than M 7 and subsequent associated damage to buildings and heavy causalities within the metropolitan area. We strongly suggest that building resistance requirements in Ulaanbaatar should be revised to mitigate for the potential of extensive seismic damage. The results of this study can be used to revise the seismic hazard map and stipulate a new disaster prevention strategy to improve public safety in Ulaanbaatar. It is also possible that there may be other active faults in the vicinity of Ulaanbaatar, and these require investigation.

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