scholarly journals Neotectonic analysis, active stress field and active faults seismic hazard assessment in Western Crete

2017 ◽  
Vol 47 (2) ◽  
pp. 582 ◽  
Author(s):  
D. Mountrakis ◽  
A. Kilias ◽  
A. Pavlaki ◽  
C. Fassoulas ◽  
E. Thomaidou ◽  
...  
Keyword(s):  
Stress Field ◽  
Seismic Hazard ◽  
Hazard Assessment ◽  
Hazard Analysis ◽  
Active Faults ◽  
Seismic Hazard Assessment ◽  
Fault Zones ◽  
Extension Phase ◽  
Fault System ◽  
Normal Faults

Within the framework of this study the complicated fault system of Western Crete was napped in detail and its kinematic and dynamic setting was analysed in order to distinguish 13 major active and possible active fault zones, the seismic potential of which was assessed. Moreover, kinematic data and striations were used to estimate the corresponding stress field geometry. Two stress phases were recognized: 1st the N-S extension phase (D1) in Mid-Upper Miocene to Lower Pliocene times forming E-W normal faults that bound the Neogene basins; 2nd the E-W extension phase (D2) in Late Pliocene-recent times forming N-S trending active normal faults. Smaller, mainly NE-SW trending faults, with significant strike-slip component, indicate a kinematic compatibility to the D2 phase, acting as transfer faults between larger N-S fault zones. The faults were incorporated in a detailed seismic hazard analysis together with the available seismological data, involving both probabilistic and deterministic approaches, for seismic hazard assessment of several selected sites (municipalities).

Locating fault tips to aid fault length identification: an example from the Gulf of Corinth rift

2020 ◽  
Author(s):  
Jenni Robertson ◽  
Gerald Roberts ◽  
Francesco Iezzi ◽  
Marco Meschis ◽  
Delia Gheorghiu ◽  
...  
Keyword(s):  
Seismic Hazard ◽  
Hazard Assessment ◽  
Seismic Hazard Assessment ◽  
Fault System ◽  
Normal Faults ◽  
Probabilistic Seismic Hazard Assessment ◽  
Maximum Magnitude ◽  
Gulf Of Corinth ◽  
Exposure Ages ◽  
Fault Length

<p>Crustal-scale active normal faults dominate seismic hazard in some regions and have been intensely studied. However, the lateral tips of these structures have received relatively little attention in the literature so their geometries are poorly known. This is an important omission because locating the tips of normal faults is vital in order to define fault lengths and calculate maximum expected earthquake magnitudes. Identifying tips will be challenging if their geometries, kinematics and rates of deformation are poorly known. Consequently, incorrectly identified tips and hence fault lengths may contribute to uncertainty in Probabilistic Seismic Hazard Assessment.</p><p>We investigate the geometry, rates and kinematics of active normal faulting in the western tip zone of the South Alkyonides Fault System (SAFS) (Gulf of Corinth, Greece) by detailed fault mapping and fault offset dating using a combination of new <sup>234</sup>U/<sup>230</sup>Th coral ages and in situ <sup>36</sup>Cl cosmogenic exposure ages on wave-cut platforms deformed by faults.</p><p>Our results reveal that there is no clear singular fault tip and that distributed deformation in the tip zone of the SAFS occurs across as many as eight faults arranged within ~700 m across strike, each of which deforms deposits and landforms associated with the 125 ka marine terrace of Marine Isotope Stage 5e. Summed throw-rates across strike achieve values as high as 1.6 mm/yr, values that approach those close to the centre of the crustal-scale fault of 2-3 mm/yr from Holocene palaeoseismology and 3-4 mm/yr from GPS geodesy. Considering the uncertainty in the location of the western tip induced by distributed faulting, the SAFS fault length is uncertain by up to ± 6%, which equates to a total maximum magnitude uncertainty of Mw 0.1.</p><p>The calculated tip displacement gradient summed across parallel faults since 125 ka for the western tip zone of the SAFS is within the upper range compared to data from other normal crustal-scale faults. We discuss stress interaction between the SAFS and a neighbouring along-strike crustal-scale fault as a potential cause of the observed fault complexity and anomalously high throw and investigate this by undertaking Coulomb stress transfer modelling. The results from the study are discussed within the context of fault-based seismic hazard assessment.</p><p> We conclude that identifying the locations of fault tips is challenging. While the results of this study may or may not be typical of other tip zones owing to the interaction, there is a need for further studies that explore the geometry of both non-interacting and interacting fault tip zones.</p>

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 Identifikasi Sesar Aktif di Pulau Bali dengan Menggunakan Data Pemetaan Geologi Permukaan dan Morfologi Tektonik

2021 ◽  
Vol 35 (1) ◽  
pp. 45
Author(s):  
Hurien Helmi ◽  
Gayatri Indah Marliyani ◽  
Siti Nur’aini
Keyword(s):  
Hazard Analysis ◽  
Active Faults ◽  
Fault System ◽  
Normal Faults ◽  
Earthquake Hazards ◽  
Digital Elevation ◽  
Shallow Earthquakes ◽  
Lineament Analysis ◽  
Elevation Model ◽  
Back Arc

Pulau Bali dan sekitarnya berada dekat dengan zona subduksi sehingga rawan terhadap bencana gempa bumi. Struktur utama yang menyebabkan gempa bumi di Bali umumnya berada di zona subduksi di bagian selatan dan di zona sesar naik belakang busur di utara yang dikenal dengan sesar naik Flores. Selain potensi gempa dari kedua zona sesar ini, gempa yang berasal dari zona sesar di darat juga bisa menimbulkan bahaya yang signifikan. Penelitian ini bertujuan untuk melakukan pemetaan sesar aktif di darat dengan menggunakan kombinasi antara metode penginderaan jauh dengan survey lapangan. Data yang digunakan sebagai peta dasar adalah data digital elevation (DEM) model DEMNAS beresolusi 8 m serta data DEM beresolusi 0.5 m yang dihasilkan melalui proses fotogrametri dari foto udara. Analisis kelurusan menunjukkan adanya pola berarah baratlaut-tenggara dan timulaut-baratdaya. Validasi di lapangan menunjukkan bahwa kelurusan ini berasosiasi dengan keberadaan sesar-sesar geser, sesar oblique dan sesar turun. Sesar-sesar ini memotong batuan berumur Kuarter hingga endapan masa kini. Selain itu, data sebaran seismisitas menunjukkan adanya zona kegempaan dangkal yang berada pada area di sekitar kelurusan yang dipetakan. Kedua indikator ini menunjukkan bahwa sesar-sesar yang teridentifikasi dalam penelitian ini bisa dikategorikan sebagai sesar aktif. Hasil dari penelitian ini memberikan pemahaman baru mengenai geometri sesar aktif yang ada di Pulau Bali dan potensi kegempaan di masa yang akan datang yang memberikan kontribusi terhadap upaya mitigasi bencana gempa bumi di Pulau Bali. Bali and its surrounding region are located within proximity of the Sunda-Banda subduction zone making it prone to earthquake hazards. The structures that caused earthquakes in Bali are mainly from the front subduction faults and from the back-arc thrust fault known as the Flores Fault. In addition, earthquakes are frequently occur in the inland fault system. This study aims to map the inland active faults in Bali using a combination of remotely-based and field-mapping methods. We use the 8-m resolution digital elevation model (DEM) of DEMNAS and the 0.5 m resolution DEM from photogrammetry processing of aerial photo as our base maps. Our lineament analysis identifies northwest-southeast and northeast-southwest lineaments. Our field observation confirms these lineaments to be associated with strike-slip, oblique and normal faults. These faults dissect Quarternary to recent rock units. In addition, seismicity data indicate the occurrence of shallow earthquakes in the vicinity of these structures. All of these indicate that these structures are active. Results from this study provide a new understanding of the inland active fault geometry in Bali, useful in the seismic hazard analysis and may contribute to the earthquake mitigation efforts in Bali.   

scholarly journals MAPPING OF THE NW-TRENDING HIDDEN FAULTS FROM ANALYSIS OF THE RELIEF AND GEOPHYSICAL FIELDS IN THE PRIAMURYE REGION

2021 ◽  
Vol 40 (3) ◽  
pp. 54-66
Author(s):  
T.V. Merkulova ◽  
◽  
G.Z. Gil’manova ◽  
S.A. Tusikova ◽  
◽  
...  
Keyword(s):  
Seismic Hazard ◽  
Hazard Assessment ◽  
Seismic Hazard Assessment ◽  
Seismic Energy ◽  
Magnetic Anomalies ◽  
Fault Zones ◽  
Geophysical Fields ◽  
Lower Rank

The paper investigates indications of the NW-trending hidden faults in the Priamurye region. Four maijor fault zones and a series of lower-rank faults are mapped, which are indicated by lineaments of the relief, magnetic anomalies and arranged earthquake foci sequences. The NW-trending faults control the block divisibility of the upper part of the lithosphere in the region and are currently seismically active. Two NW-trending hidden faults are characterized by a considerable amount of the seismic energy released which should be accounted for in the seismic hazard assessment of the region.

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.

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.

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