scholarly journals 25,000 Years long seismic cycle in a slow deforming continental region of Mongolia

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Laurent Bollinger ◽  
Yann Klinger ◽  
Steven L. Forman ◽  
Odonbaatar Chimed ◽  
Amgalan Bayasgalan ◽  
...  
Keyword(s):  
Seismic Hazard ◽  
Active Faults ◽  
Ground Surface ◽  
Slip Rate ◽  
Seismic Hazard Assessment ◽  
Return Time ◽  
Fault Behavior ◽  
Seismogenic Structures ◽  
Cumulative Deformation ◽  
Large Earthquakes

AbstractThe spatial distribution of large earthquakes in slowly deforming continental regions (SDCR) is poorly documented and, thus, has often been deemed to be random. Unlike in high strain regions, where seismic activity concentrates along major active faults, earthquakes in SDCR may seem to occur more erratically in space and time. This questions classical fault behavior models, posing paramount issues for seismic hazard assessment. Here, we investigate the M7, 1967, Mogod earthquake in Mongolia, a region recognized as a SDCR. Despite the absence of visible cumulative deformation at the ground surface, we found evidence for at least 3 surface rupturing earthquakes during the last 50,000 years, associated with a slip-rate of 0.06 ± 0.01 mm/year. These results show that in SDCR, like in faster deforming regions, deformation localizes on specific structures. However, the excessive length of return time for large earthquakes along these structures makes it more difficult to recognize earthquake series, and could conversely lead to the misconception that in SDCR earthquakes would be randomly located. Thus, our result emphasizes the need for systematic appraisal of the potential seismogenic structures in SDCR in order to lower the uncertainties associated with the seismogenic sources in seismic hazard models.

scholarly journals 25,000 Years Long Seismic Cycle in a Slow Deforming Continental Region of Mongolia

2021 ◽  
Author(s):  
Laurent Bollinger ◽  
Yann Klinger ◽  
Steven Forman ◽  
Odonbaatar Chimed ◽  
Amgalan Bayasgalan ◽  
...  
Keyword(s):  
Seismic Hazard ◽  
Active Faults ◽  
Ground Surface ◽  
Slip Rate ◽  
Seismic Hazard Assessment ◽  
Return Time ◽  
Fault Behavior ◽  
Seismogenic Structures ◽  
Cumulative Deformation ◽  
Large Earthquakes

Abstract The spatial distribution of large earthquakes in Slowly Deforming Continental Regions (SDCR) is poorly documented and, thus, has often been deemed to be random. Unlike in high strain regions, where seismic activity concentrates cyclically along major active faults, earthquakes in SDCR may seem to occur more erratically in space and time. This questions classical fault behavior models, posing paramount issues for seismic hazard assessment. Here, we investigate the M7, 1967, Mogod earthquake in Mongolia, a region recognized as a SDCR. Despite the absence of visible cumulative deformation at the ground surface, we found evidence for at least 3 surface rupturing earthquakes during the last 50,000 years, associated to a slip-rate of 0,06 ± 0,01 mm/yr. These results show that in SDCR, like in faster deforming regions, deformation localizes on specific structures. However, the excessive length of return time for large earthquakes along these structures makes it more difficult to recognize earthquake series, and could conversely lead to the misconception that in SDCR earthquakes would be randomly located. Thus, our result emphasizes the need for systematic appraisal of the potential seismogenic structures in SDCR in order to lower the uncertainties associated with the seismogenic sources in seismic hazard models.

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.

Database of active faults in Slovenia: geologic input into seismic hazard assessment at national scale

2021 ◽  
Author(s):  
Jure Atanackov ◽  
Petra Jamšek Rupnik ◽  
Miloš Bavec ◽  
Bogomir Celarc ◽  
Jernej Jež ◽  
...  
Keyword(s):  
Seismic Hazard ◽  
Hazard Assessment ◽  
Active Faults ◽  
Seismic Hazard Assessment ◽  
National Scale

scholarly journals Methodology for Earthquake Rupture Rate estimates of fault networks: example for the Western Corinth Rift, Greece

2017 ◽  
Author(s):  
Thomas Chartier ◽  
Oona Scotti ◽  
Hélène Lyon-Caen ◽  
Aurélien Boiselet
Keyword(s):  
Active Faults ◽  
Slip Rate ◽  
Seismic Hazard Assessment ◽  
System Level ◽  
Fault System ◽  
Normal Faults ◽  
Accurate Estimation ◽  
Probabilistic Seismic Hazard Assessment ◽  
Earthquake Rupture ◽  
Multiple Faults

Abstract. Modelling the seismic potential of active faults is a fundamental step of probabilistic seismic hazard assessment (PSHA). An accurate estimation of the rate of earthquakes on the faults is necessary in order to obtain the probability of exceedance of a given ground motion. Most PSHA studies consider faults as independent structures and neglect the possibility of multiple faults or fault segments rupturing simultaneously (Fault to Fault -FtF- ruptures). The latest Californian model (UCERF-3) takes into account this possibility by considering a system level approach rather than an individual fault level approach using the geological , seismological and geodetical information to invert the earthquake rates. In many places of the world seismological and geodetical information long fault networks are often not well constrained. There is therefore a need to propose a methodology relying only on geological information to compute earthquake rate of the faults in the network. In this methodology, similarly to UCERF-3, a simple distance criteria is used to define FtF ruptures and consider single faults or FtF ruptures as an aleatory uncertainty. Rates of earthquakes on faults are then computed following two constraints: the magnitude frequency distribution (MFD) of earthquakes in the fault system as a whole must follow an imposed shape and the rate of earthquakes on each fault is determined by the specific slip-rate of each segment depending on the possible FtF ruptures. The modelled earthquake rates are then confronted to the available independent data (geodetical, seismological and paleoseismological data) in order to weigh different hypothesis explored in a logic tree. The methodology is tested on the Western Corinth Rift, Greece (WCR) where recent advancements have been made in the understanding of the geological slip rates of the complex network of normal faults which are accommodating the ~15 mm/yr North-South extension. Modelling results show that geological, seismological extension rates and paleoseismological rates of earthquakes cannot be reconciled with only single fault rupture scenarios and require hypothesising a large spectrum of possible FtF rupture sets. Furthermore, in order to fit the imposed regional Gutenberg-Richter MFD target, some of the slip along certain faults needs to be accommodated either with interseismic creep or as post-seismic processes. Furthermore, individual fault’s MFDs differ depending on the position of each fault in the system and the possible FtF ruptures associated with the fault. Finally, a comparison of modelled earthquake rupture rates with those deduced from the regional and local earthquake catalogue statistics and local paleosismological data indicates a better fit with the FtF rupture set constructed with a distance criteria based on a 5 km rather than 3 km, suggesting, a high connectivity of faults in the WCR fault system.

scholarly journals A seismic source zone model for the seismic hazard assessment of Slovakia

2016 ◽  
Vol 67 (3) ◽  
pp. 275-290 ◽  
Author(s):  
Jozef Hók ◽  
Robert Kysel ◽  
Michal Kováč ◽  
Peter Moczo ◽  
Jozef Kristek ◽  
...  
Keyword(s):  
Seismic Hazard ◽  
Hazard Assessment ◽  
Large Scale ◽  
Seismic Hazard Assessment ◽  
Seismic Source ◽  
Source Zone ◽  
Zone Model ◽  
Geological Structures ◽  
Seismotectonic Model ◽  
Seismogenic Structures

Abstract We present a new seismic source zone model for the seismic hazard assessment of Slovakia based on a new seismotectonic model of the territory of Slovakia and adjacent areas. The seismotectonic model has been developed using a new Slovak earthquake catalogue (SLOVEC 2011), successive division of the large-scale geological structures into tectonic regions, seismogeological domains and seismogenic structures. The main criteria for definitions of regions, domains and structures are the age of the last tectonic consolidation of geological structures, thickness of lithosphere, thickness of crust, geothermal conditions, current tectonic regime and seismic activity. The seismic source zones are presented on a 1:1,000,000 scale map.

scholarly journals Active fault databases: building a bridge between earthquake geologists and seismic hazard practitioners, the case of the QAFI v.3 database

2017 ◽  
Vol 17 (8) ◽  
pp. 1447-1459 ◽  
Author(s):  
Julián García-Mayordomo ◽  
Raquel Martín-Banda ◽  
Juan M. Insua-Arévalo ◽  
José A. Álvarez-Gómez ◽  
José J. Martínez-Díaz ◽  
...  
Keyword(s):  
Seismic Hazard ◽  
Active Fault ◽  
Slip Rate ◽  
Seismic Hazard Assessment ◽  
Recurrence Interval ◽  
Maximum Magnitude ◽  
Geological Evidence ◽  
Seismic Parameters ◽  
Standard Quality

Abstract. Active fault databases are a very powerful and useful tool in seismic hazard assessment, particularly when singular faults are considered seismogenic sources. Active fault databases are also a very relevant source of information for earth scientists, earthquake engineers and even teachers or journalists. Hence, active fault databases should be updated and thoroughly reviewed on a regular basis in order to keep a standard quality and uniformed criteria. Desirably, active fault databases should somehow indicate the quality of the geological data and, particularly, the reliability attributed to crucial fault-seismic parameters, such as maximum magnitude and recurrence interval. In this paper we explain how we tackled these issues during the process of updating and reviewing the Quaternary Active Fault Database of Iberia (QAFI) to its current version 3. We devote particular attention to describing the scheme devised for classifying the quality and representativeness of the geological evidence of Quaternary activity and the accuracy of the slip rate estimation in the database. Subsequently, we use this information as input for a straightforward rating of the level of reliability of maximum magnitude and recurrence interval fault seismic parameters. We conclude that QAFI v.3 is a much better database than version 2 either for proper use in seismic hazard applications or as an informative source for non-specialized users. However, we already envision new improvements for a future update.

scholarly journals Neotectonic activity and paleoseismological analysis in Eastern of Antioquia, in the vicinity of Medellin city - Colombia

2015 ◽  
pp. 5-19
Author(s):  
Albeiro De Jesús Rendón-Rivera ◽  
John Jairo Gallego-Montoya ◽  
Jenny Paola Jaramillo-Rendón ◽  
Adrián González-Patiño ◽  
José Humberto Caballero-Acosta ◽  
...  
Keyword(s):  
Seismic Hazard ◽  
Age Of Onset ◽  
Active Faults ◽  
Seismic Hazard Assessment ◽  
Seismic Events ◽  
Small Surface ◽  
Neotectonic Activity ◽  
Neotectonic Deformation ◽  
Alluvial Terraces ◽  
Prehistoric Earthquakes

The aim of this investigation was the paleoseismological characterization of eastern Antioquia, using trenches analysis and detailed study of indicators of neotectonic activity, some of which had been reported in previous seismic hazard assessment studies of the Aburra Valley.Through techniques of neotectonic, paleoseismology and also age correlation of Quaternary deposits obtained by several authors, it was found at Alcaravanes site (Marinilla Town), evidences of three seismic events with magnitudes Mw 6.4, 6.6 and 6.5 which displaced recent deposits with maximum ages of 440,000, 37,000 and 8,000 years respectively. Likewise, two prehistoric earthquakes, both with magnitude Mw 6.5 were recognized at the Hamburgo site (Guarne Town), dated between 880,000 and 37,000 years respectively, which proves the existence and activity of La Mosca fault. Finally, the Manantiales site (Rionegro Town) revealed a couple of seismic events with magnitude Mw 6.7 and 6.6 that displaced alluvial terraces in Rio Negro basin with a maximum age of onset of neotectonic deformation of 880,000 years.Latest neotectonic findings change the perspective of seismic hazard in Medellin city and surroundings. Prehistoric earthquakes have occurred in the last million years and created small surface rupture and faulting not related with active mountain fronts. Furthermore, the evidence shows obliterated active faults and efficiency of erosion factors in modeling relief and alluvial fill in the basins of Rionegro Erosion Surface.

Across-strike variations of fault slip-rates constrained using in-situ cosmogenic 36Cl concentrations.

2020 ◽  
Author(s):  
Francesco Iezzi ◽  
Gerald Roberts ◽  
Joanna Faure Walker ◽  
Ioannis Papanikolaou ◽  
Athanassios Ganas ◽  
...  
Keyword(s):  
Seismic Hazard ◽  
Strain Rate ◽  
Active Faults ◽  
Slip Rate ◽  
High Temporal Resolution ◽  
Strain Rates ◽  
Time Intervals ◽  
The Holocene ◽  
Regional Strain

<p>It is important to constrain the spatial distribution of strain-rate in deforming continental material because this underpins calculations of continental rheology and seismic hazard. To do so, it is becoming increasingly common to use combinations of GPS and historical and instrumental seismicity data to constrain regional strain-rate fields. However, GPS geodetic sites, whether permanent or campaign stations, tend to be widely-spaced relative to the spacing of active faults with known Holocene offsets. At the same time, the interpretation of seismicity data can be difficult due to lack of historical seismicity in cases where local fault recurrence intervals are longer than the historical record. This causes uncertainty on how regional strain-rates are partitioned in time and space, and hence with uncertainty regarding calculations of continental rheology and seismic hazard. To overcome this issue, we have gained high temporal resolution slip-rate histories for three parallel faults using in situ <sup>36</sup>Cl cosmogenic dating of the exposure of three parallel normal fault planes that have been progressively exhumed by earthquakes. We study the region around Athens, central Greece, where there also exists a relatively-dense GPS network and extensive records of instrumental and historical earthquakes. This allows to compare regional, decadal strain-rates measured with GPS geodesy with strain-rates across the faults implied by slip since ~40,000 years BP. We show that faults have all had episodic behaviour during the Holocene, with alternating earthquake clusters and periods of quiescence through time. Despite the fact that all three faults have been active in the Holocene, each fault slips in discrete time intervals lasting a few millennia, so that only one fault accommodates strain at any time. We show that magnitudes of strain-rates during the high slip-rate episodes are comparable with the regional strain-rates measured with GPS (fault strain-rates are 50-100% of the value of GPS regional strain-rate). Thus, if the GPS-derived strain-rate applies over longer time intervals, it appears that single faults dominate the strain-accumulation at any given time, with crustal deformation and seismic hazard localised within a distributed network of faults.</p><p> </p>

scholarly journals Measurements of tectonic micro-displacements within the Idrija fault zone in the Učja valley (W Slovenia)

2020 ◽  
Vol 60 (1) ◽  
Author(s):  
Andrej Gosar
Keyword(s):  
Fault Zone ◽  
Active Fault ◽  
Average Rate ◽  
Active Faults ◽  
Slip Rate ◽  
Seismic Hazard Assessment ◽  
Vertical Displacements ◽  
Recent Activity ◽  
Insight Into ◽  
Horizontal Displacements

A recent slip-rate of an active fault is a very important seismotectonic parameter, but not easy to determine. Idrija fault, 120 km long, is a prominent geomorphologic feature with large seismogenic potential, still needed to be researched. Measurements of tectonic micro-displacements can provide insight into its recent activity. The Učja valley extends transversally to the Idrija fault and was therefore selected for the installation of TM 71 extensometer. Measurements on the crack within its inner fault zone are conducted from the year 2004. In 14 years of observations a systematic horizontal displacements with average rate of 0.21 mm/year and subordinate vertical displacements of 0.06 mm/year were established, proving the activity of this fault. An overview of methods of displacement measurements related to active faults and of newer interdisciplinary investigations of the Idrija fault is given. Displacement rates are beside for geodynamic interpretations important for improvement of seismotectonic models and thus for better seismic hazard assessment.

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