Characterizing seismic sources is crucial for assessing seismic hazards, particularly for active faults like the Kachchh Mainland Fault (KMF), a 150 km long fault in the Kachchh region. The KMF is ...laterally displaced by transverse faults with different orientations (NW-SE to NE-SW). To better understand the KMF, a joint interpretation of the five North-South trending Magnetotelluric (MT) profiles (two recently acquired profiles and three earlier published ones) is conducted across various segments of the fault. These profiles covered diverse stretches across the fault, ranging from 15 to 81 km in length. Analysis of the geoelectric sections derived from 2-D MT data inversion revealed that the KMF dips to the south in the vicinity of the transverse faults while it takes on a steep north-dipping orientation farther away from the transverse faults. The central and eastern parts of the KMF are seismically active. Therefore, seismic hazard assessments is carried out by considering a magnitude Mw 7.6 scenario earthquake with a northward dip for all four segments of the KMF. To account for uncertainty, parametric testing was conducted, exploring a range of stress drop values, Kappa values, and quality factors (Q) as proposed by various studies in the Kachchh region. The maximum peak ground acceleration (PGA), of 0.85 g (under soft rock conditions with Vs of 500 m/s), is estimated due to the considered scenario earthquake along all four segments. The study revealed that the PGA decreased by 14–38% at sites south of the KMF (such as Bhuj and Bhachau) and increased by 30–47% at sites located north of the KMF (like Rapar and Khavda) compared to estimates based on a southward dipping KMF. This underlines the significance of considering and estimating variations in fault dip along its length and how such variations can impact seismic hazard assessments within tectonic plate interiors.
•Kachchh Mainland Fault (KMF) is characterized by five magnetotelluric profiles along its entire length.•The study finds that KMF dips north but changes sharply near a transverse fault to steep south.•Segment-specific dip and strike values are used to estimate seismic hazard due to KMF in Kachchh region.•Significant variation in seismic hazard (up to ∼40%) is observed due to revised dip direction (north instead of previously assumed south).
New geological and morphotectonic surface data coupled with the revision of the ENI-Exploration & Production seismic lines, made it possible to review the tectonic structure of the ...Pliocene-Quaternary front of the eastern Southern Alps in the area between the Cellina River and the Tagliamento River (central Carnic Prealps, NE Italy). The eastern Southern Alps are a SE-verging fold and thrust belt in activity from the middle Miocene to the Present. The presence of Paleogene structural inheritances influenced the current structural arrangement of the thrust-belt and the potential seismogenesis, supporting segmentation of the Neoalpine external front. In particular, the presence of the NW-SE trending Mt.Ciaurlec – Palmanova – Pozzuolo structural high, inherited from the W-ward propagation of the External Dinarides during Paleogene, generated lateral lithological facies change and influenced not only the undulation between the Neogene-Quaternary Maniago-Meduno and Toppo-Forgaria Thrusts, but also the segmentation of the outermost portion of the Neoalpine external front consisting into two segments with different geometric and structural characteristics: 1) the ENE-WSW striking Arba-Sequals segment that runs buried under the upper Pleistocene sequences of the piedmont Friuli plain; 2) the W-E Ragogna segment that shows widespread evidence of surface deformation of the Last Glacial Maximum (LGM) alluvial plain. In particular, the long-lasting activity of the Ragogna segment is testified by the late Miocene-Middle Pleistocene angular unconformities, forced drainage anomalies and tilted and uplifted Quaternary palaeosurfaces. A discussion on the seismogenic potential of the investigated structures is proposed.
•The active front of eastern Southern Alps in the carnic Prealps (NE Italy) is segmented.•The Paleogene inheritances influenced the present structural architecture of ESA Neogene-Quaternary active front.•Seismogenic potential of each active structure has been evaluated.
A nearly 20-year hiatus in major seismic activity in southern California ended on 4 July 2019 with a sequence of intersecting earthquakes near the city of Ridgecrest, California. This sequence ...included a foreshock with a moment magnitude (
) of 6.4 followed by a
7.1 mainshock nearly 34 hours later. Geodetic, seismic, and seismicity data provided an integrative view of this sequence, which ruptured an unmapped multiscale network of interlaced orthogonal faults. This complex fault geometry persists over the entire seismogenic depth range. The rupture of the mainshock terminated only a few kilometers from the major regional Garlock fault, triggering shallow creep and a substantial earthquake swarm. The repeated occurrence of multifault ruptures, as revealed by modern instrumentation and analysis techniques, poses a formidable challenge in quantifying regional seismic hazards.
The increase in seismic activity after a large-magnitude earthquake coupled with the reduction in the lateral load-carrying capacity of the affected structures presents a significant human and ...financial risk to communities. The focus of this paper is placed on quantifying the impact of both the elevated post-mainshock seismic hazard as well as the mainshock-induced structural damage on the seismic risk of three reinforced concrete moment frame structures. The seismic hazard due to sequential earthquakes is examined in both pre- and post-mainshock environments. The time-dependent nature of seismic hazard in the post-mainshock environment is accounted for through the adoption of a Markov risk assessment framework. In the post-mainshock environment, the seismic risk is examined as a function of the time elapsed since the mainshock’s occurrence while in the pre-mainshock environment, the risk is investigated during an assumed lifespan of 50 years for the studied structures. For the buildings and the high-seismicity site used in this study, both the increased post-mainshock seismic hazard as well as the reduction in the structural capacity are found to have a great influence on the seismic risk. The substantial contribution of aftershocks to the collapse risk in the pre-mainshock environment highlights the need for a design procedure that accounts for the additional seismic risk from aftershocks.
The heterogeneous South American geology has coined a wide variety of neotectonic settings where crustal seismogenic sources do occur. This fact has led to different approaches for mapping and ...inventory neotectonic structures. The South American Risk Assessment project promoted the discussion and update under uniform standards of the available information on neotectonic deformation, for its application in regional Probabilistic Seismic Hazard Assessments. As a result, 1533 hazardous faults have been inventoried onshore South America, 497 of them qualifying to feed the engine model driving probabilistic maps.
Main hazardous structures are concentrated throughout the eastern boundary of the Northern Andean Sliver and along the foreland-facing Andean Thrust Front. Space geodesy and seismicity illuminate the seismogenic significance of these deformation belts, although few neotectonic surveys have been conducted to date in the latter region. The characteristics of the main structures or deformation zones are here outlined according to their filiation to neotectonic domains, which are dependant on the geologic, seismotectonic, or morphotectonic settings in Andean and extra-Andean regions.
The knowledge accrued on the hazardous faults in South America here compiled, reinforces the fact that some of these structures constitute significant hazard sources for many urban areas and critical facilities and should be incorporated in seismic hazard assessments. However, the available fault data are insufficient in many cases or carry significant epistemic uncertainties for fault source characterization. This contribution aims to summarize the present knowledge on the South American hazardous faults as well as the main challenges for successful fault data incorporation into seismic hazard models.
Retraction: “Control of Multiple Detachments on Structural Development in the Southern Junggar Fold‐and‐Thrust Belt, Northern Tian Shan: Implications for Seismic Hazard Assessment,” by J. Qiu, G. ...Rao, Y. Yu, X. Wang, Z. Peng, L. Gao, D. Yang, L. Xiao, Q. Yao, https://doi.org/10.1029/2021TC006712. The above article from Tectonics, published online on 3 August 2021 in Wiley Online Library (wileyonlinelibrary.com), has been retracted by agreement between the authors; the journal Editor‐in‐Chief, Taylor Schildgen; Wiley Periodicals, LLC; and the American Geophysical Union. The retraction has been agreed due to the need to restructure seismic interpretations and structural modeling that resulted in significant technical errors throughout the article.
Machine learning (ML) has evolved rapidly over recent years with the promise to substantially alter and enhance the role of data science in a variety of disciplines. Compared with traditional ...approaches, ML offers advantages to handle complex problems, provide computational efficiency, propagate and treat uncertainties, and facilitate decision making. Also, the maturing of ML has led to significant advances in not only the main-stream artificial intelligence (AI) research but also other science and engineering fields, such as material science, bioengineering, construction management, and transportation engineering. This study conducts a comprehensive review of the progress and challenges of implementing ML in the earthquake engineering domain. A hierarchical attribute matrix is adopted to categorize the existing literature based on four traits identified in the field, such as ML method, topic area, data resource, and scale of analysis. The state-of-the-art review indicates to what extent ML has been applied in four topic areas of earthquake engineering, including seismic hazard analysis, system identification and damage detection, seismic fragility assessment, and structural control for earthquake mitigation. Moreover, research challenges and the associated future research needs are discussed, which include embracing the next generation of data sharing and sensor technologies, implementing more advanced ML techniques, and developing physics-guided ML models.
Liquefaction is one of the earthquake-related hazards commonly experienced during earthquake occurrences in the Philippines. A database of liquefaction occurrences in the Philippines was developed ...through the analysis of historical documents, reports, catalogs, newspaper articles, and eyewitness interviews. A total of 808 liquefaction accounts were analyzed—798 of which were induced by 110 earthquakes that occurred from 1619 to 2020, with magnitudes ranging from M 5.1 to 8.3. The database also contains three undated liquefaction accounts from paleoseismic investigations, and seven liquefaction accounts related to four volcanic eruptions. The liquefaction occurrences in the accounts were analyzed in terms of their location quality, liquefaction features, probability ranking, and geomorphic units. We observed that liquefaction can occur repeatedly at the same sites that liquefied during past earthquakes and volcanic activities. This database may be used for seismic hazard studies and disaster risk reduction and mitigation purposes.
During an earthquake the seismic wave amplification related to local site conditions can have a significant impact on the ground motion. In order to account for these local effects some proxies for ...the soil characteristics exist; e.g., the average shear-wave velocity of the upper 30 m (VS,30), or the equivalent shear-wave velocity from the ground to the depth of the seismic bedrock when this is less than 30 m VS,eq.
The aim of this paper is to provide maps of seismic shallow soil classification for Italy accounting for two sources of information: site-specific measurements and large-scale geological maps. The soil maps are obtained via a four-step procedure: (1) a database of available site-specific investigations is built, covering (unevenly) the whole national territory; (2) twenty geo-lithological complexes are identified from the available geological maps; (3) the investigations are grouped as a function of the geo-lithological complex and the distribution of measured VS,30 and VS,eq are estimated; (4) medians and standard deviations of such distributions are assumed to be representative of the corresponding complexes. The statistics of investigations are used to derive the large-scale soil maps. To make the results of the study available, a stand-alone software has been developed. Despite not being adequate substitutes of site-specific studies such as microzonation and local site response analyses, the provided results can be useful for large-scale seismic risk studies.
•Procedure for correlating surface geological maps and Vs measurements.•Maps of large-scale seismic soil classification for Italy.•Site classification according to EC8 and ItBC2018.•Stand-alone software for database interrogation.
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