Trench investigations through the trace of the 1980 El Asnam thrust fault: Evidence for paleoseismicity

1988 ◽  
Vol 78 (2) ◽  
pp. 979-999
Author(s):  
M. Meghraoui ◽  
H. Philip ◽  
F. Albarede ◽  
A. Cisternas
Keyword(s):  
Late Holocene ◽  
Slip Rate ◽  
Thrust Fault ◽  
Recurrence Time ◽  
Normal Faults ◽  
Tectonic Event ◽  
Vertical Movements ◽  
Radiocarbon Dates ◽  
Flood Deposits ◽  
Large Earthquakes

Abstract During the EI Asnam earthquake of 10 October 1980 (Ms = 7.3), a clear active thrust fault with left-lateral offset was observed. Three trenches have been excavated across this fault in order to determine slip rate and recurrence intervals between large earthquakes, and thus reconstruct its past activity. Exposure I was excavated in the flood area created in 1980 by a pressure ridge across the Cheliff and Fodda Rivers. Six flood deposits (silty-sandy and muddy horizons) alternating with paleosoils appear in this exposure; they are affected by normal faults associated with the main thrust fault. Assuming that every flood deposit results from a tectonic event of magnitude greater than 7, we can correlate previous flood deposits with these events. Exposures II and III display thrust faults displacing different paleosoils. We propose a sequence of reconstructions based on the thickness of the various deposits and the dip-slip of each tectonic event. The Late Holocene slip rate is 0.65 mm/yr for the dip-slip and 0.46 mm/yr for each of the horizontal and the vertical movements. Radiocarbon dates of coseismic movements indicate a rather irregular seismic activity during the past 7000 yr. Two sequences of large earthquakes around 4000 yr B.P. and around the modern age are separated with a period of quiescence. The average Late Holocene recurrence interval of large earthquakes is 1061 yr; however, during the active faulting episodes, the recurrence time varies from approximately 300 to 500 yr.

The probability of large earthquakes cannot be calculated from seismicity rates

2020 ◽  
Author(s):  
Max Wyss
Keyword(s):  
Seismic Waves ◽  
Slip Rate ◽  
Strike Slip ◽  
Magnitude Scale ◽  
Recurrence Time ◽  
Normal Faults ◽  
Earthquake Probability ◽  
San Andreas ◽  
Seismicity Rates ◽  
Large Earthquakes

<p>The hypothesis that extrapolation of the Gutenberg-Richter (GR) relationship allows estimates of the probability of large earthquakes is incorrect. For nearly 200 faults for which the recurrence time, T<sub>r</sub> (1/probability of occurrence), is known from trenching and geodetically measured deformation rates, it has been shown that T<sub>r</sub> based on seismicity is overestimated typically by one order of magnitude or more. The reason for this is that there are not enough earthquakes along major faults. In some cases there are too few earthquakes for the fault to be mapped based on seismicity. Some examples are the following rupture segments of great faults: the 1717 Alpine Fault, the 1856 San Andreas, the 1906 San Andreas, the 2001 Denali earthquakes, for which geological Tr are 100 years to 300 years and seismicity T<sub>r</sub> are 10,000 to 100,000 years. In addition, the hypothesis leads to impossible results when one considers the dependence of the b-value on stress. It has been shown that thrusts, strike-slip and normal faults have low, intermediate and high b-values, respectively. This implies that, regardless of local slip rates, the probability of large earthquakes predicted by the hypothesis is high, intermediate and low in thrust, strike-slip, and normal faulting, respectively. Measurements of recurrence probability show a different dependence: earthquake probability depends on slip rate. Finally, the hypothesis predicts different probabilities for large earthquakes, depending on the magnitude scale used. For the 1906 rupture segment, the difference in probability of an M8 earthquake is approximately a factor of 50, using the two available catalogs. Various countries measure earthquake magnitude on their own scale that is intended to agree with the M<sub>L</sub> scale of California or the M<sub>S</sub> scale of the USGS. However, it is not trivial to match a scale that is valid for a different region with different attenuation of seismic waves. As a result, some regional M-scales differ from the global M<sub>S</sub> scale, which yields different T<sub>r</sub> for the same Mmax in the same region, depending on whether the global or local magnitude scale is used. Based on the aforementioned facts, the hypothesis that probabilities of large earthquakes can be estimated by extrapolating the GR relationship has to be abandoned.</p>

scholarly journals 1855 and 1991 surveys of the San Andreas fault: Implications for fault mechanics

1994 ◽  
Vol 84 (2) ◽  
pp. 241-246
Author(s):  
Lisa B. Grant ◽  
Andrea Donnellan
Keyword(s):  
Late Holocene ◽  
San Andreas Fault ◽  
Slip Rate ◽  
Large Earthquake ◽  
Fault Mechanics ◽  
Radiocarbon Dates ◽  
Apparent Slip ◽  
San Andreas ◽  
Main Fault ◽  
Fault Trace

Abstract Two monuments from an 1855 cadastral survey that span the San Andreas fault in the Carrizo Plain have been right-laterally displaced 11.0 ± 2.5 m by the 1857 Fort Tejon earthquake and associated seismicity and afterslip. This measurement confirms that at least 9.5 ± 0.5 m of slip occurred along the main fault trace, as suggested by measurements of offset channels near Wallace Creek. The slip varied by 2 to 3 m along a 2.6-km section of the main fault trace. Using radiocarbon dates of the penultimate large earthquake and measurements of slip from the 1857 earthquake, we calculate an apparent slip rate for the last complete earthquake cycle that is at least 25% lower than the late-Holocene slip rate on the main fault trace. Comparison of short-term broad-aperture strain accumulation rates with the narrow-aperture late-Holocene slip rate indicates that the fault behaves nearly elastically over a time scale of several earthquake cycles. Therefore, slip in future earthquakes should compensate the slip-rate deficit from the 1857 earthquake.

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.

Complex Slip Distribution of the 2021 Mw 7.4 Maduo, China, Earthquake: An Event Occurring on the Slowly Slipping Fault

2021 ◽  
Author(s):  
Rumeng Guo ◽  
Hongfeng Yang ◽  
Yu Li ◽  
Yong Zheng ◽  
Lupeng Zhang
Keyword(s):  
Slip Rate ◽  
Slip Distribution ◽  
Seismic Gap ◽  
Seismogenic Fault ◽  
Coseismic Slip ◽  
Slip Rates ◽  
Kunlun Mountain ◽  
Coulomb Failure ◽  
Main Fault ◽  
Large Earthquakes

Abstract The 21 May 2021 Maduo earthquake occurred on the Kunlun Mountain Pass–Jiangcuo fault (KMPJF), a seismogenic fault with no documented large earthquakes. To probe its kinematics, we first estimate the slip rates of the KMPJF and Tuosuo Lake segment (TLS, ∼75 km north of the KMPJF) of the East Kunlun fault (EKLF) based on the secular Global Positioning System (GPS) data using the Markov chain Monte Carlo method. Our model reveals that the slip rates of the KMPJF and TLS are 1.7 ± 0.8 and 7.1 ± 0.3 mm/yr, respectively. Then, we invert high-resolution GPS and Interferometric Synthetic Aperture Radar observations to decipher the fault geometry and detailed coseismic slip distribution associated with the Maduo earthquake. The geometry of the KMPFJ significantly varies along strike, composed of five fault subsegments. The most slip is accommodated by two steeply dipping fault segments, with the patch of large sinistral slip concentrated in the shallow depth on a simple straight structure. The released seismic moment is ∼1.5×1020  N·m, equivalent to an Mw 7.39 event, with a peak slip of ∼9.3 m. Combining the average coseismic slip and slip rate of the main fault, an earthquake recurrence period of ∼1250−400+1120  yr is estimated. The Maduo earthquake reminds us to reevaluate the potential of seismic gaps where slip rates are low. Based on our calculated Coulomb failure stress, the Maduo earthquake imposes positive stress on the Maqin–Maqu segment of the EKLF, a long-recognized seismic gap, implying that it may accelerate the occurrence of the next major event in this region.

Tectonics and recent seismicity near Flathead Lake, Montana

1982 ◽  
Vol 72 (5) ◽  
pp. 1591-1599
Author(s):  
Anthony Qamar ◽  
Jerry Kogan ◽  
Michael C. Stickney
Keyword(s):  
Ice Sheet ◽  
Normal Faults ◽  
Earthquake Swarms ◽  
Flathead Lake ◽  
Glacial Processes ◽  
Cordilleran Ice Sheet ◽  
Large Earthquakes ◽  
East West

abstract Since 1900, more than 290 earthquakes have been reported near Flathead Lake, Montana. Surprisingly, none has exceeded magnitude 5 to 512. Most recent earthquake swarms appear to result from east-west or northwest-southeast extension along short fault segments west and north of the lake. Major normal faults like the Swan and Mission faults east of the lake may pose higher risk, but they appear dormant today. Deformation of sediments in Flathead Lake may be caused by several large earthquakes more than 10,000 years ago but is more probably due to glacial processes accompanying the last retreat of the Cordilleran ice sheet.

Late Pleistocene extension and strike-slip in the Dead Sea Basin

2004 ◽  
Vol 141 (5) ◽  
pp. 565-572 ◽  
Author(s):  
YUVAL BARTOV ◽  
AMIR SAGY
Keyword(s):  
Internal Structure ◽  
Slip Rate ◽  
Dead Sea ◽  
Strike Slip ◽  
Normal Faults ◽  
Small Scale ◽  
Dead Sea Basin ◽  
Pull Apart Basin ◽  
Western Border ◽  
The Dead

A newly discovered active small-scale pull-apart (Mor structure), located in the western part of the Dead Sea Basin, shows recent basin-parallel extension and strike-slip faulting, and offers a rare view of pull-apart internal structure. The Mor structure is bounded by N–S-trending strike-slip faults, and cross-cut by low-angle, E–W-trending normal faults. The geometry of this pull-apart suggests that displacement between the two stepped N–S strike-slip faults of the Mor structure is transferred by the extension associated with the normal faults. The continuing deformation in this structure is evident by the observation of at least three deformation episodes between 50 ka and present. The calculated sinistral slip-rate is 3.5 mm/yr over the last 30 000 years. This slip rate indicates that the Mor structure overlies the currently most active strike-slip fault within the western border of the Dead Sea pull-apart. The Mor structure is an example of a small pull-apart basin developed within a larger pull-apart. This type of hierarchy in pull-apart structures is an indication for their ongoing evolution.

scholarly journals The cryptic seismic potential of blind faults revealed by off-fault geomorphology, Pichilemu, Chile.

2020 ◽  
Author(s):  
Julius Jara-Muñoz ◽  
Daniel Melnick ◽  
Anne Socquet ◽  
Joaquin Cortés-Aranda ◽  
Dominik Brill ◽  
...  
Keyword(s):  
Slip Rate ◽  
Active Regions ◽  
Seismic Hazards ◽  
Recurrence Time ◽  
Diagnostic Features ◽  
Seismic Potential ◽  
Megathrust Earthquakes ◽  
Marine Terraces ◽  
Stress Changes ◽  
Geomorphic Features

Abstract In seismically-active regions, mapping capable faults and estimating their recurrence time is the first step to assess seismic hazards. Fault maps are commonly based on geologic and geomorphic features evident at the surface; however, mapping blind faults and estimating their seismic potential is challenging because on-fault diagnostic features are absent. Here, we study the Pichilemu Fault in coastal Chile, unknown until it generated a M7.0 earthquake in 2010. The lack of evident surface faulting suggests a partly-hidden blind fault. Using off-fault deformed marine terraces, we estimate a slip-rate of 0.42 ± 0.04 m/ka, which when integrated with deformation estimated from satellite geodesy during the 2010 earthquake suggests a 2.5 ± 0.25 ka recurrence time for M6.6-6.9 extensional earthquakes. We propose that extension is associated with stress changes during megathrust earthquakes and accommodated by sporadic slip during upper-plate earthquakes. Our results have implications for assessing the seismic potential of cryptic faults along seismically-active coasts.

scholarly journals Geomorphic evidence of recent activity along the Vodice thrust fault in the Ljubljana Basin (Slovenia) – a preliminary study

2014 ◽  
Vol 56 (6) ◽  
Author(s):  
Petra Jamšek Rupnik ◽  
Lucilla Benedetti ◽  
Frank Preusser ◽  
Miloš Bavec ◽  
Marko Vrabec
Keyword(s):  
Slip Rate ◽  
Surface Expression ◽  
Thrust Fault ◽  
Luminescence Dating ◽  
Quaternary Sediments ◽  
Infrared Stimulated Luminescence ◽  
Recent Activity ◽  
The Town ◽  
Geomorphological Analysis ◽  
Central Slovenia

<p>We investigated two prominent, <strong><sup>~</sup></strong>E-W trending scarps in Quaternary sediments, located close to the town of Vodice in the Ljubljana Basin (central Slovenia). By using detailed geomorphological analysis of the scarps, field surveying, and structural observations of deformed Quaternary sediments, we conclude that the scarps are the surface expression of a N-dipping thrust fault that has been active during the Quaternary. From Optically Stimulated Luminescence and Infrared Stimulated Luminescence dating of deformed Quaternary sediments we estimate a slip rate of 0.1 to 0.3 mm a<sup>-1 </sup>in the last 133 ka. Using the published empirical fault-scaling relationships, we estimate that an earthquake of magnitude 5.9 to 6.5 may be expected on the Vodice thrust fault. The fault may, therefore, present a major seismic hazard for the densely populated and urbanised region of central Slovenia.</p>

scholarly journals Detection of Large Holocene Earthquakes in the Sedimentary Record of Wellington, New Zealand, Using Diatom Analysis

2021 ◽  
Author(s):  
◽  
Ursula Alyson Cochran
Keyword(s):  
New Zealand ◽  
Late Holocene ◽  
Weighted Averaging ◽  
Diatom Analysis ◽  
Sedimentary Record ◽  
Sedimentary Sequences ◽  
Quantitative Estimates ◽  
Modern Analogue ◽  
Environmental Transitions ◽  
Large Earthquakes

<p>New Zealand is situated on the boundary between the Pacific and Australian tectonic plates. The Wellington region lies near the southern end of the Hikurangi subduction zone and within a zone of major, active strike-slip faults. Wellington's paleoseismic and historic records indicate that large surface rupture earthquakes have occurred on these faults in the past. Development of a complete record of past large earthquakes is a high priority for the region because of the risk posed by occurrence of large earthquakes in the future. The existing paleoseismic record has been derived predominantly from studies of fault trench stratigraphy, raised beach ridges and offset river terraces. The sedimentary record of lakes and coastal waterbodies is a source of information that has not been used specifically for paleoseismic purposes in the region. Therefore investigation of Wellington's sedimentary record is used in this thesis to make a contribution to the paleoseismic record. Holocene sedimentary sequences are studied from three small, low elevation, coastal waterbodies: Taupo Swamp, Okupe Lagoon and Lake Kohangapiripiri. Sequences of between 200 and 650 cm depth were collected using a hand-operated coring device. Sedimentology and diatom microfossil content were analysed and interpreted to enable reconstruction of paleoenvironment at each site. Radiocarbon dating was used to provide chronologies for the sequences that are aged between 5000 and 7500 calibrated years before present (cal. years BP). Diatom analysis is the main tool used to reconstruct paleoenvironment and detect evidence for occurrence of past large earthquakes. To aid reconstruction of sedimentary sequences used in this project, as well as coastal sequences in New Zealand in general, a coastal diatom calibration set was constructed using 50 sites around New Zealand. Modern diatom distribution and abundance, and associated environmental variables are analysed using ordination and weighted averaging techniques. Detrended correspondence analysis arranges species according to salinity preferences and divides sites clearly into waterbody types along a coastal gradient. This analysis enables reconstruction of waterbody type from fossil samples by passive placement onto ordination diagrams. Weighted averaging regression of calibration set samples results in a high correlation (r2jack=0.84) between observed and diatom inferred salinity, and enables salinity preferences and tolerances to be derived for 100 species. This confirms for the first time that species' preferences derived in the Northern Hemisphere are generally applicable to diatoms living in the coastal zone of New Zealand. Weighted averaging calibration and the modern analogue technique are used to generate quantitative estimates of paleosalinity for fossil samples. Paleoenvironmental reconstructions of Taupo Swamp, Okupe Lagoon and Lake Kohangapiripiri indicate that each waterbody has been isolated from the sea during the late Holocene. Isolation has been achieved through interplay of sediment accumulation causing growth of barrier beaches, and coseismic uplift. Ten distinct transitions between different paleoenvironments are recognised from the three sequences. These transitions involve changes in relative sea level or water table level often in association with catchment disturbance or marine influx events. All transitions occur suddenly and are laterally extensive and synchronous within each waterbody. Quantitative estimates of paleosalinity and waterbody type are used to differentiate between large and small magnitude changes in paleoenvironment. Five transitions involve large amounts of paleoenvironmental change and provide evidence for earthquakes occurring at approximately 5200, approximately 3200, and approximately 2300 cal. years BP. Five other transitions are consistent with the effects of large earthquakes occurring at approximately 6800, 2200, approximately 1000, approximately 500 cal. years BP and 1855 AD but do not provide independent evidence of the events. Environmental transitions at Lake Kohangapiripiri clarify the timing of rupture of the Wairarapa Fault by bracketing incompatible age estimates derived from two different sites on the fault. The oldest environmental transitions recognised at Taupo Swamp and Okupe Lagoon both occur at approximately 3200 cal. years BP indicating that western Wellington was uplifted at this time. Environmental transitions are recorded at all three study sites at approximately 2300 cal. years BP indicating that the entire western and central Wellington region experienced coseismic uplift at this time. Because of the distance between sites this apparent synchroneity implies that several faults in the region ruptured at a similar time. Investigation of sedimentary sequences contributes to the existing paleoseismic record by providing additional estimates of timing for past large earthquakes, enabling estimation of the areal extent of the effects of past earthquakes, and by highlighting periods of fault rupture activity in the late Holocene.</p>

Repeated Folding during Late Holocene Earthquakes on the La Cal Thrust Fault near Mendoza City (Argentina)

2013 ◽  
Vol 103 (2A) ◽  
pp. 936-949 ◽  
Author(s):  
E. Salomon ◽  
S. Schmidt ◽  
R. Hetzel ◽  
F. Mingorance ◽  
A. Hampel
Keyword(s):  
Late Holocene ◽  
Thrust Fault
Sign in / Sign up

Export Citation Format

Share Document