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.

Taking up the challenge of identifying active faults for seismic hazard assessment of the city of Ulaanbaatar (Mongolia)

2020 ◽  
Author(s):  
Abeer Al Ashkar ◽  
Antoine Schlupp ◽  
Matthieu Ferry ◽  
Munkhuu Ulziibat
Keyword(s):  
Seismic Hazard ◽  
Regional Scale ◽  
Active Faults ◽  
Seismic Hazard Assessment ◽  
Capital City ◽  
Sensor Data ◽  
Tectonic Geomorphology ◽  
Stream Channels ◽  
Tectonic Structures ◽  
The City

<p>Ulaanbaatar, capital city of Mongolia (1.5 M inhabitants, i.e. half of the country’s population), is located in Central Mongolia where seismic activity and deformation rates are low (< 1mm/yr.). In contrast, Western Mongolia has experienced four great earthquakes (M ≥ 8) between 1905 and 1957 as well as numerous moderate ones. Some (e.g. the 1957 Bogd earthquake) have been felt at the capital located more than 500 km away. During the last decades, several active faults, located 10 km to 45 km away from Ulaanbaatar, have been discovered and studied. Tectonic Geomorphology and Paleoseismology studies indicate that these faults are able to generate earthquakes of M ≥ 6 with average recurrence times ranging from 1 kyr to 10 kyr (e.g. 1195 ± 157 yr for the Sharkhai fault). Furthermore, since 2005 very dense microseismicity swarms located 10 km NW of the City have been monitored by the Seismic Observatory of Mongolia (IAG). Further studies showed the swarms are produced by the previously undetected Emeelt fault zone along three parallel branches. Due to their proximity to a key population and economic center, all these active structures contribute significantly to increasing Seismic Hazard. During the course of these studies, we documented Quaternary activity along several supplementary faults, which demonstrates that the knowledge of active faults in the region is still incomplete and suggests seismic hazard levels should be revised. Therefore, we undertook to map, as exhaustively as possible, all active tectonic structures in a radius of 300 km around Ulaanbaatar. Here we present preliminary results based on the combined analysis of multi-source and multi-sensor data from satellite images (e.g. Pleiades, Sentinel-2, Landsat8), UAV photographs, and digital elevation models (TanDEM-X and UAV photogrammetric DEMs) in order to extract the most relevant information at various scales. We performed a detailed Tectonic Geomorphology analysis of alluvial and slope landforms to identify recent deformation affecting stream channels and associated deposits (ponds, fans and terraces). On that basis, we document segmentation, deformation patterns and kinematics, as well as relationships between faults at regional scale. Finally, we identify potential sites for future paleoseismic investigations along the main structures. Though this project is in a preliminary stage, our long-term goal is to build a comprehensive database of sources of seismic hazard to the City of Ulaanbaatar and integrate these results into seismic hazard calculations.</p>

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 Geodetic fault slip rates on active faults in the Baza sub-Basin (SE Spain): Insights for seismic hazard assessment

2021 ◽  
Vol 144 ◽  
pp. 101815
Author(s):  
P. Alfaro ◽  
A. Sánchez-Alzola ◽  
I. Martin-Rojas ◽  
F.J. García-Tortosa ◽  
J. Galindo-Zaldívar ◽  
...  
Keyword(s):  
Seismic Hazard ◽  
Hazard Assessment ◽  
Active Faults ◽  
Seismic Hazard Assessment ◽  
Fault Slip ◽  
Se Spain ◽  
Slip Rates ◽  
Fault Slip Rates

scholarly journals Implications from palaeoseismological investigations at the Markgrafneusiedl Fault (Vienna Basin, Austria) for seismic hazard assessment

2017 ◽  
Author(s):  
Esther Hintersberger ◽  
Kurt Decker ◽  
Johanna Lomax ◽  
Christopher Lüthgens
Keyword(s):  
Seismic Hazard ◽  
Hazard Assessment ◽  
Active Faults ◽  
Seismic Hazard Assessment ◽  
Vienna Basin ◽  
Slip Rates ◽  
Small Surface ◽  
Strong Earthquakes ◽  
Splay Faults ◽  
Magnitude Estimates

Abstract. Including faults into seismic hazard assessment depends strongly on their level of seismic activity. Intraplate regions are characterized by low seismicity, so that the evaluation of existing earthquake catalogues does not necessarily reveal all active faults that contribute to seismic hazard. In the Vienna Basin (Austria), moderate historical seismicity (Imax/Mmax = 8/5.2) concentrates along the left-lateral strike-slip Vienna Basin Transfer Fault (VBTF). In contrast, several normal faults branching out of the VBTF show neither historical nor instrumental earthquake records, although geomorphological data indicate Quaternary displacement along those faults. Here, we present a palaeoseismological dataset of three trenches crossing one of these splay faults, the Markgrafneusiedl Fault (MF), in order to evaluate the seismic potential of the fault. Comparing the observations of the different trenches, we found evidence for 5–6 major surface-breaking earthquakes during the last 120 ka, with the youngest event occurring at around ~ 14 ka before present. The inferred surface displacements lead to magnitude estimates ranging between M = 6.2 ± 0.3 and M = 6.8 ± 0.1. Data can be interpreted by two possible event lines, with event line 1 showing more regular recurrence intervals of about 20–25 ka between the earthquakes with M ≥ 6.5, and event line 2 indicating that such earthquakes cluster in two time intervals in the last 120 ka. Event line 2 appears more plausible. Trench observations also show that structural and sedimentological records of strong earthquakes with small surface offset have only low conservation potential. Vertical slip rates of 0.03–0.04 mm/a derived from the trenches compare well to geomorphically derived slip rates of 0.015–0.085 mm/a. Magnitude estimates from fault dimensions suggest that the largest earthquakes observed in the trenches activated the entire fault surface of the MF including the basal detachment that links the normal fault with the VBTF. The most important implications of these paleoseismological results for seismic hazard assessment are that: (1) The MF needs to be considered as a seismic source irrespective of the fact that it did not release historical earthquakes. (2) The maximum credible earthquakes in the Vienna Basin should be considered to be about M = 7.0. (3) The MF is kinematically and geologically equivalent to a number of other splay faults of the VBTF. It must be assumed that these faults are potential sources of large earthquakes as well. The frequency of strong earthquakes near Vienna is therefore expected to be significantly higher than the earthquake frequency reconstructed for the MF.

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.

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.

scholarly journals Bayesian probabilities for occurrence of large earthquakes in the seismogenic sources of Japan and Phillipine during the period 1998-2017

2001 ◽  
Vol 34 (4) ◽  
pp. 1619
Author(s):  
T. M. TSAPANOS ◽  
O. CH. GALANIS ◽  
S. D. MAVRIDOU ◽  
M. P. HELMl
Keyword(s):  
Seismic Hazard ◽  
Bayesian Statistics ◽  
Poisson Distribution ◽  
Bayesian Approach ◽  
Seismic Sources ◽  
Time Interval ◽  
Seismogenic Sources ◽  
The One ◽  
Large Earthquakes ◽  
The Bayesian Approach

The Bayesian statistics is adopted in 11 seismic sources of Japan and 14 of Philippine in order to estimate the probabilities of occurrence of large future earthquakes, assuming that earthquakes occurrence follows the Poisson distribution. The Bayesian approach applied represents the probability that a certain cut-off magnitude (or larger) will exceed in a given time interval of 20 years, that is 1998-2017. This cut-off magnitude is chosen the one with M=7.0 or greater. In this case we can consider these obtained probabilities as a seismic hazard presentation. More over curves are produced which present the fluctuation of the seismic hazard between these seismic sources. These graphs of varying probability are useful either for engineering or other practical purposes

Tectonic geomorphology of High Zagros Ranges, SW Iran: an initiative towards seismic hazard assessment

2015 ◽  
Vol 74 (4) ◽  
pp. 3007-3017 ◽  
Author(s):  
Ali Faghih ◽  
Akbar Esmaeilzadeh Soudejani ◽  
Ahmad Nourbakhsh ◽  
Sara Rokni
Keyword(s):  
Seismic Hazard ◽  
Hazard Assessment ◽  
Seismic Hazard Assessment ◽  
Tectonic Geomorphology ◽  
Sw Iran
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