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.

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 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.

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.

Updated seismotectonic zoning scheme of Metropolitan France, with reference to geologic and seismotectonic data

2013 ◽  
Vol 184 (3) ◽  
pp. 225-259 ◽  
Author(s):  
Stéphane Baize ◽  
Edward Marc Cushing ◽  
Francis Lemeille ◽  
Hervé Jomard
Keyword(s):  
Seismic Hazard ◽  
Hazard Assessment ◽  
Active Faults ◽  
Seismic Hazard Assessment ◽  
Tectonic Activity ◽  
Hazard Evaluation ◽  
Boundary Location ◽  
Seismotectonic Zones ◽  
Seismic Hazard Evaluation ◽  
Surface Geology

Abstract This work presents the seismotectonic zoning scheme of Metropolitan France developed by the IRSN (French Institute for Radioprotection and Nuclear Safety) within the framework of its seismic hazard assessment activities. It is the outcome of many years of work following the publication of the “seismotectonic atlas” in 1993 [Grellet et al., 1993]. This scheme supports the assessment of seismic hazard by IRSN. It takes into account the most recent data concerning the deep and surface geology, as well as those related to seismotectonics and tectonic activity. It finally includes 67 surface seismotectonic zones (STZ), as well as a catalogue of 74 faults or structures (named hereafter “potential active faults”) for which indications of Neogene to Quaternary displacement can be inferred. The description of the zoning scheme comes along with an estimation of the uncertainty on the boundary location between adjacent STZ. We also qualitatively determine a “relevance order” for each limit, so as to illustrate their reliability to separate regions of different seismogenic potential. Also, we attributed to the faults an indication whose purpose is to reflect the recent character of their activity, and thus their seismotectonic potential. This assessment of uncertainties was undertaken to better integrate the zoning scheme in the general approach, which arises from recent studies, namely the propagation of the uncertainties in seismic hazard evaluation, whether deterministic or probabilistic.

Seismotectonic regions for Germany - Concept and results

2020 ◽  
Author(s):  
Tim Hahn ◽  
Jonas Kley ◽  
Diethelm Kaiser ◽  
Thomas Spies ◽  
Jörg Schlittenhardt ◽  
...  
Keyword(s):  
Seismic Hazard ◽  
Source Region ◽  
Active Faults ◽  
Seismic Hazard Assessment ◽  
Source Area ◽  
Geological Structure ◽  
Time Slice ◽  
Geological Time ◽  
Geological Evidence ◽  
Lithospheric Thickness

<p>Seismotectonic regions are a basic input in seismic hazard assessment. Several seismotectonic regionalizations for Germany were proposed in the past. We are presently developing a new regionalization based on the definition in the Safety Standard of the Nuclear Safety Standards Commission KTA 2201.1 (2011-11): “A seismotectonic unit is a region for which uniformity is assumed regarding seismic activity, geological structure and development and, in particular, regarding neotectonic conditions. A seismotectonic unit may also be an earthquake source region.” Our new concept focusses on a transparent implementation of the required geological criteria. Our approach is to initially analyze those separately from present-day seismicity. Compared to existing source area models we strive for a better documentation and justification of the geological elements used to delimit seismotectonic regions. This includes an analysis of the geological history of structures in six time slices from the Permian to the Present that will be considered in the regionalization. The time slices are (1) Permian, (2) Triassic, (3) Jurassic to Early Cretaceous, (4) Late Cretaceous, (5) Cenozoic > 20 Ma and (6) Recent (< 20 Ma). They were chosen because they are separated by marked changes of stress and kinematic regimes and were associated with the evolution of new fault systems or reactivation of existing ones. The tectonic characteristics of the time slices are briefly described.</p><p>The present-day observable fault network comprises faults from all time slices. For each time slice, a subset of active faults will be extracted based on geological evidence for fault activity at that time, e.g. syntectonic deposits. The uncertainties of these age assignments will be documented. The fault subset will be used to estimate overall kinematics, a paleo-stress field and to delimit little deformed or stable areas. Faults, kinematics, stress and stable areas can then be compared to present-day seismicity/active faults, slip directions, stress and undeformed areas as well as other parameters such as crustal and lithospheric thickness. These steps are repeated for each time slice. The superposition of active faults and stable regions across all time slices will identify faults prone to reactivation and regions that remained undeformed over geological time, potentially indicating areas of increased or reduced present-day seismic hazard.</p><p>A comparison with seismicity of the last 1000 years shows partial agreement between regions of strong (or repeated) deformation and regions of higher seismicity. On the other hand, stronger earthquakes occasionally cluster in regions appearing stable since Permian time, the Anglo-Brabant Massif being a prominent example of this type.</p>

scholarly journals Seismic hazard for the Trans Adriatic Pipeline (TAP). Part 2: broadband scenarios at the Fier Compressor Station (Albania)

2021 ◽  
Author(s):  
L. Moratto ◽  
A. Vuan ◽  
A. Saraò ◽  
D. Slejko ◽  
C. Papazachos ◽  
...  
Keyword(s):  
Seismic Hazard ◽  
Ground Motion ◽  
Hazard Assessment ◽  
Transfer Functions ◽  
Active Faults ◽  
Seismic Hazard Assessment ◽  
Probabilistic Seismic Hazard Assessment ◽  
Compressor Station ◽  
Damage Functions ◽  
Worst Case

AbstractTo ensure environmental and public safety, critical facilities require rigorous seismic hazard analysis to define seismic input for their design. We consider the case of the Trans Adriatic Pipeline (TAP), which is a pipeline that transports natural gas from the Caspian Sea to southern Italy, crossing active faults and areas characterized by high seismicity levels. For this pipeline, we develop a Probabilistic Seismic Hazard Assessment (PSHA) for the broader area, and, for the selected critical sites, we perform deterministic seismic hazard assessment (DSHA), by calculating shaking scenarios that account for the physics of the source, propagation, and site effects. This paper presents a DSHA for a compressor station located at Fier, along the Albanian coastal region. Considering the location of the most hazardous faults in the study site, revealed by the PSHA disaggregation, we model the ground motion for two different scenarios to simulate the worst-case scenario for this compressor station. We compute broadband waveforms for receivers on soft soils by applying specific transfer functions estimated from the available geotechnical data for the Fier area. The simulations reproduce the variability observed in the ground motion recorded in the near-earthquake source. The vertical ground motion is strong for receivers placed above the rupture areas and should not be ignored in seismic designs; furthermore, our vertical simulations reproduce the displacement and the static offset of the ground motion highlighted in recent studies. This observation confirms the importance of the DSHA analysis in defining the expected pipeline damage functions and permanent soil deformations.

scholarly journals A detailed seismic zonation model for shallow earthquakes in the broader Aegean area

2013 ◽  
Vol 1 (6) ◽  
pp. 6719-6784 ◽  
Author(s):  
D. A. Vamvakaris ◽  
C. B. Papazachos ◽  
C. Papaioannou ◽  
E. M. Scordilis ◽  
G. F. Karakaisis
Keyword(s):  
Seismic Hazard ◽  
Hazard Assessment ◽  
Active Faults ◽  
Seismic Hazard Assessment ◽  
Maximum Magnitude ◽  
Seismic Zone ◽  
Seismic Zonation ◽  
Aegean Area ◽  
Seismic Zones ◽  
Shallow Earthquakes

Abstract. In the present work we present an effort to define a new seismic zonation model of area type sources for the broader Aegean area, which can be readily used for seismic hazard assessment. The definition of this model is based not only on seismicity information but incorporates all available seismotectonic and neotectonic information available for the study area, in an attempt to define zones which show not only a rather homogeneous seismicity release but also exhibit similar active faulting characteristics. For this reason, all available seismological information such as fault plane solutions and the corresponding kinematic axes have been incorporated in the analysis, as well as information about active tectonics, such as seismic and active faults. Moreover, various morphotectonic features (e.g. relief, coastline) were also considered. Finally, a revised seismic catalogue is employed and earthquake epicentres since historical times (550 BC–2008) are considered, in order to define areas of common seismotectonic characteristics, that could constitute a discrete seismic zone. A new revised model of 113 earthquake seismic zones of shallow earthquakes for the broader Aegean area is finally proposed. Using the proposed zonation model, a detailed study is performed for the catalogue completeness for the recent instrumental period. Using the defined completeness information, seismicity parameters (such as G–R values) for the 113 new seismic zones have been calculated, and their spatial distribution was also examined. The spatial variation of the obtained b values shows an excellent correlation with the geotectonic setting in the area, in good agreement with previous studies. Moreover, a quantitative estimation of seismicity is performed in terms of the mean return period, Tm, of large (M ≥ 6.0) earthquakes, as well as the most frequent maximum magnitude, Mt, for a typical time period (T = 50 yr), revealing significant spatial variations of seismicity levels within the study area. The new proposed seismic zonation model and its parameters can be readily employed for seismic hazard assessment for the broader Aegean area.

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