Paleoseismological Studies Research Articles

A comparative study of bedrock fault scarps by s-UAV and t-LiDAR: Insights into site selection criteria for paleo-seismology studies

Normal fault scarps, as classical topographic features and geomorphological markers along mountain range-fronts, form in consolidated bedrock due to faulting in extensional settings. They generally preserve more complete records of paleo-earthquakes than fault scarps in unconsolidated sediments. The reconstruction of paleo-seismic history from a bedrock fault scarp in terms of the times, co-seismic slips and ages by a combination of quantitative morphological analysis, TCNs dating and other physical/chemical index has been proven feasible by several previous studies. However, this success heavily relies on a suitable site selection along the bedrock fault scarp because geomorphic processes are also capable exhuming the fault surface, i.e., an erosion-origin fault surface. To distinguish between tectonic- and fault-origin fault surfaces, four bedrock fault surfaces (MJYC, NMZC, DYC and SYC) in the northern Shanxi Rift have been targeted to carry out a comparative study by combining small unmanned aerial vehicle (s-UAV) surveys and terrestrial laser scanning (TLS). The results can be classified into two groups according to their quantified morphological characteristics and exposed ways. For the NMZC and SYC group, which are in elevated areas away from gullies, the quantitative morphological analysis shows that both bedrock fault surfaces have the characteristics of vertical segmentation. This kind of segmentation indicates that the fault surfaces may be exhumed by repeated seismic events, and the corresponding co-seismic slips are determined by the height of these segments. For the MJYC and DYC group, the quantitative morphology shows a gradually-changing characteristic without segmentation. This gradually-changing characteristic indicates an erosional exposure mode from geomorphic processes, and accordingly the paleo-seismic information cannot be extracted. Thus, results from this study highlights the importance of selecting a suitable study site when conducting paleo-seismic research on bedrock faults. Based on experience obtained in this study combined with previous cases, we propose the characteristics of bedrock fault surfaces suitable for extracting paleo-seismic information and corresponding identification principles. Finally, a general workflow for paleo-earthquake history reconstruction from bedrock fault scarps is proposed to promote paleo-earthquake study in bedrock areas.

Evaluating the coulomb static stress change and fault interaction in an extensional intra-volcanic arc: 1000 years of earthquake history in the Acambay Graben, Trans-Mexican Volcanic Belt

One of the main challenges in slow slip-rate intra-continental fault systems is evaluating which fault could generate the next large earthquake. Therefore, it is crucial to characterize the spatiotemporal distribution of the seismicity and to understand the influence of moderate to large earthquakes on successive events. The Acambay Graben, in the central part of the Trans-Mexican Volcanic Belt, is an intra-continental normal fault system and the source of the 1912 Acambay earthquake (mb = 6.9) that ruptured mainly the Acambay-Tixmadejé fault as well as other fault segments of the graben. Paleoseismological studies have identified earlier events significant events produced by other graben faults, such as the Venta de Bravo Fault event occurred between 1026 and 1700 CE. In this study, we model the static Coulomb stress transfer related to the 1026–1700 and the 1912 CE events showing that the older event may have set the conditions to induce or accelerate the historical 1912 Acambay earthquake. In the same way, this last event could have triggered the Maravatío earthquake (February 22, 1979, Mw = 5.3). Furthermore, the cumulative variation of the Coulomb stress (Ev1 = 0.5–10 bar, Ev2 = 5–30 bar, Ev3 = 0.5–1 bar) corresponding to the three events reveals a spatial correlation between the areas that have experienced an increase in static stress with the regional distribution of the instrumental seismicity. The obtained results suggest that some active faults of the graben, which have accumulated static stress during the last 1000 years, are potential sources for the next fault rupture, i.e., faults that would need to be better studied and characterized. This information is of great importance to improve the seismic hazard assessment and risk estimations in the heavily populated Central Mexico region with more than 24 million people and better understand the fault interaction in slow slip-rate intra-continental fault systems.

Active faults, Paleoseismological trenching and seismic hazard assessment in the Northern Mygdonia Basin, Northern Greece: The Assiros-Krithia fault and the Drimos fault zone

The Plio-Quaternary Mygdonia Basin in Northern Greece is bounded by active normal faults that can host significant earthquakes and produce considerable damage to the city of Thessaloniki (the second biggest city in Greece – 1 million population), located only 15–20 km away. In 1978, a damaging M = 6.5 earthquake occurred along a fault in the southern part of the basin, generating primary and secondary surface ruptures. This manuscript offers the results of the first detailed geomorphological and paleoseismological investigations in the northern part of the basin. As a result: i) a new active normal fault has been mapped, the Assiros-Krithia fault (AKF); and ii) another fault zone that has been assessed with probable activity in the literature, the Drimos fault zone (DFZ), has been confirmed active and mapped in detail. Paleoseismological trenching investigations supported by radiometric dating were carried out along both structures. The AKF and DFZ form the northern and northwestern boundaries of the Mygdonia Basin, respectively. The AKF deflects the local drainage network and is expressed as a single north dipping localised fault trace, gently uplifting the northern part of the Mygdonia Basin. The last event produced 48 cm of vertical displacement around 4540 cal. yrs BP, and the fault has an estimated slip rate of ∼0.1 mm/yr. The DFZ is an 8-10 km-long NW-SE trending normal fault that dips and downthrows to the NE (045o-050o). It is characterised by distributed deformation across eight major and secondary fault planes. Four of these planes have been activated over the last 9000 years, therefore the structure is Holocene active. The DFZ has an estimated slip rate of 0.1–0.3 mm/yr and may merged with the Liti-Gerakarou fault zone in multi-segment ruptures. The DFZ highlights that NW-SE trending faults are potentially active in Northern Greece. Their long recurrence intervals justify why they were not activated during the period covered by the historical record and emphasise, once again, the necessity of paleoseismological studies and the implementation of fault specific approaches in seismic hazard assessment.

Soft sediment deformation features in Dauki Fault region: evidence of paleoearthquakes, Shillong Plateau, NE India

The northeastern region (NER) of India has several complex regional geological structures, out of which the Dauki fault (DF) is a prominent one. The E–W trending reverse DF, which is inferred to go through the southern margin of Shillong Plateau (SP), has played major role in the regional deformation of the adjoining areas and was believed to be active during the Late Quaternary time. Previous paleoseismological studies conducted on the eastern and western part of the DF, Bangladesh, revealed that the fault ruptured in AD 849–920 and AD 1548, respectively. However, there were no studies on the DF from southern side of the SP, India. For the first time, from Indian side, soft sediment deformation structures (SSDS) are reported from five trenches in and around the DF zone, SP. Close to the Dauki village, five trenches in the eastern part of the DF, SP, show micro faulting, sand dykes, disturbed strata, and water escape structures. The detailed investigation of SSDS indicates that the origin of deformation is seismic trigger. The 14C AMS dating of deformation structures generated by earthquakes suggests three seismic events occurred between 130 and 920 year BP, 5415 to 9140 year BP, and at about 4285 year BP. This study confirms that DF is indeed active, at least, since the mid-Holocene. More trenching and dating of seismically induced deformation features are needed to accurately calculate the recurrence interval of significant earthquakes that can strike the fast-expanding urban areas in India and Bangladesh.

Updated historical earthquake catalog of İzmir region (western Anatolia) and its importance for the determination of seismogenic source

Although destructive earthquakes have not occurred in the instrumental period except for the 30 October 2020 Samos earthquake (Mw = 6.6), the records show that there were significant earthquakes that caused great destruction in İzmir and its surroundings in the historical period. However, it is not yet clear which faults are causative for these earthquakes affecting İzmir and its surroundings. For this purpose, it has been attempted to determine new geological, seismological and environmental data by examining a large number of original sources, records and old international earthquake catalogs, other than the existing national catalogs used in seismicity studies in Turkey. In this context, a new local and updated historical earthquake catalog was prepared for İzmir and its immediate vicinity. The data obtained from the records show that the maximum intensity of some destructive historical earthquakes in the İzmir region was X. This means that the active faults in İzmir and its immediate vicinity have the potential to generate earthquakes of up Mw = 7.1 in the future. Details on historical earthquakes strengthen the possibility that these earthquakes may have been generated by active faults located near the İzmir city settlement. The isoseismic maps created for the first time using historical data, point out that the highest seismic intensity in the 178, 1688 and 1778 A.D. earthquakes caused destruction in the İzmir city center and nearby settlements indicate that they were concentrated at a relatively small area in the Bay of İzmir, and tectonically in the hanging-wall of the İzmir Fault. In the most likely scenario, all these damages observed may be attributed to the western segment of the İzmir Fault (Balcova segment) since it was defined as the only seismic source around the İzmir Bay in the updated active fault map of Turkey, of course, these data should be verified by performing detailed paleoseismological studies.

Deciphering Co‐Seismic Sedimentary Processes in the Mediterranean Sea Using Elemental, Organic Carbon, and Isotopic Data

AbstractIdentification of catastrophic events recorded as resedimented deep marine deposits can be challenging because of multiple possible triggering mechanisms. This study investigates seismo‐turbidites (STs) deposited in the Ionian Sea as a consequence of major historical earthquakes related to the Calabrian Arc subduction system. Taking advantage of the available sedimentological reconstructions, we focused our analysis on high‐resolution X‐ray fluorescence core scanner (XRF‐CS), organic carbon and isotopic data to define geochemical signatures characterizing the ST units. The relationships between geochemical and sedimentological proxies were statistically tested using Pearson correlation and principal component analysis (PCA). Up to ∼78% of the total variance in the data set can be reduced to three principal components which identified four elemental ratio groups associated to the degree of terrestrial/coastal influence in each major depositional unit (i.e., pelagic, ST sandy stacked units, homogenites, tsunamite‐seiche laminites, and tsunamite backwash). The sample score results were evaluated together with organic carbon data in order to assess geochemical variability throughout the composite turbidite structure in different basins settings. The basal parts of the ST contain coarse‐grained sediment stacks whose sources can be traced back and sedimentary processes (surficial sediment erosion/massive slope failures) can be defined using geochemical data. The topmost parts of the STs exhibit a mixed compositional character suggesting basin‐wide processes such as seiche oscillations and tsunami wave erosion/backwashing. The application of selected XRF‐CS based elemental ratios as proxies in paleoseismological studies can help reconstruct the seismic history of a continental margin.

Up-to-date PSHA along the Gulf of Aqaba-Dead Sea transform fault

The Gulf of Aqaba Dead Sea Transform fault (DSTF) is a plate boundary. Its southern section separates Sinai Peninsula, Egypt and Saudi Arabia. Also, it passes through several countries. A development plan with a huge budget is drawn to develop the Gulf of Aqaba region. This plan includes the construction of King Salman Bridge. Therefore, the assessment of the seismic hazard (SH) at this seismically active region is inevitable for the sustainability of these mega projects. This paper presents a probabilistic seismic hazard assessment (PSHA) study along the DSTF. An earthquake catalogue including the paleo-seismological studies, historical records and instrumental seismicity is compiled. It is processed by converting various magnitude types to the moment magnitude (Mw) using recently derived mathematical equations. Three de-clustering techniques have been used to de-cluster the catalogue. Then, a completeness test is performed. The obtained earthquake catalogue is implemented to plot two different smoothed seismicity maps (SSMs). These maps and two areal source models are utilized to represent the seismicity along the DSTF. Five ground-motion prediction equations (GMPEs) are used to predict the ground-motion, three out of them are for the seismic sources located at shallow active crust tectonic regime and two for the intermediate depth earthquakes generating at the subduction zone south of Cyprus. The previously mentioned SH inputs are implemented through the logic-tree framework. The produced maps illustrate that the PGA values in the DSTF region range from 0.02g to 0.4g and 0.06 to 0.48 for 475 and 2475 years return period (RP), respectively. Also, seismic hazard maps using the non-de-clustered catalogue are produced.

The Late Quaternary slip-rate of the Kichera Fault (North Baikal Rift) from morphotectonic, paleoseismological and cosmogenic 10Be analyses

Late Quaternary slip rates characterize the seismic potential of an active fault in terms of estimating the average expected recurrence period for rupturing episodes. Along the Baikal Rift faults the slip rate distributions are poorly understood. This study provides morphotectonic and paleoseismological analyses of the Kichera Fault that stretches within the North Baikal Rift over a length of 100 km. Exposure ages of key displaced terraces of the Neruchanda River from in-situ produced cosmogenic 10Be depth profiles show that the highest terrace T5 is older than 315 ka, intermediate terrace T3 was abandoned 100.0 ± 30 ka ago and the lowest terrace T1 is as old as 48.3 ± 19.9 ka. These exposure ages, coupled with terrace elevation from the actual Neruchanda River bed, allow us to estimate the incision rates for the corresponding time periods which are 0.1 (maximum), 0.16 ± 0.05 and 0.19 ± 0.08 mm yr−1, respectively. Using the cumulated amplitudes of the terrace displacement, we estimate the vertical slip rates along the Kichera Fault are 0.42 ± 0.13 and 0.19 ± 0.08 mm yr−1 over the last ~100 ka and ~48.3 ka, respectively. Paleoseismological studies including morphomertic analyses of the tectonic scarp and trenching across the fault allowed estimating the age (5.4 ka) and minimum magnitude (6.8) of the last Kichera Fault rupture. Using the estimates of short- and long-term slip rates, we propose mean recurrence intervals of 5.3 and 2.4 ka, respectively. The last interval is shorter than the time since the last earthquake, indicating that the future event could be of greater magnitude to maintain the long-term average slip rate.

Earthquake history of the Yatağan Fault (Muğla, SW Turkey): implications for regional seismic hazard assessment and paleoseismology in extensional provinces

The southern part of the Western Anatolia Extensional Province is governed by E-W-trending horst-graben systems and NW-SE-oriented active faults. The NW-striking Yatağan Fault is characterised by an almost pure normal sense of motion with a minor dextral strike slip component. Although the settlements within the area have been affected by several earthquake events since ancient times (~2000 BCE), the earthquake potential and history of the Yatağan Fault has remained unknown until a few years ago. Considering the growing dense population within the area, paleoseismology studies were conducted in order to illuminate the historical earthquake activity on the Yatağan Fault. Two trenches were excavated on the fault. Structural and stratigraphic evidence from the both trenches indicated an event horizon of a paleo-earthquake that was dated between 366 and 160 BCE and 342 ± 131 CE. This event horizon most probably reflected the evidence of the latest large earthquake rupture on the Yatağan Fault.

Active fault segments along the North Anatolian Fault system in the Sea of Marmara: implication for seismic hazard

A new analysis of high-resolution multibeam and seismic reflection data, collected during several oceanographic expeditions starting from 1999, allowed us to compile an updated morphotectonic map of the North Anatolian Fault below the Sea of Marmara. We reconstructed kinematics and geometries of individual fault segments, active at the time scale of 10 ka, an interval which includes several earthquake cycles, taking as stratigraphic marker the base of the latest marine transgression. Given the high deformation rates relative to sediment supply, most active tectonic structures have a morphological expression at the seafloor, even in presence of composite fault geometries and/or overprinting due to mass-wasting or turbidite deposits. In the frame of the right-lateral strike-slip domain characterizing the North Anatolian fault system, three types of deformation are observed: almost pure strike-slip faults, oriented mainly E–W; NE/SW-aligned axes of transpressive structures; NW/SE-oriented trans-tensional depressions. Fault segmentation occurs at different scales, but main segments develop along three major right-lateral oversteps, which delimit main fault branches, from east to west: (i) the transtensive Cinarcik segment; (ii) the Central (East and West) segments; and (iii) the westernmost Tekirdag segment. A quantitative morphometric analysis of the shallow deformation patterns observed by seafloor morphology maps and high-resolution seismic reflection profiles along the entire basin allowed to determine nature and cumulative lengths of individual fault segments. These data were used as inputs for empirical relationships, to estimate maximum expected Moment Magnitudes, obtaining values in the range of 6.8–7.4 for the Central, and 6.9–7.1 for the Cinarcik and Tekirdag segments, respectively. We discuss these findings considering analyses of historical catalogues and available paleoseismological studies for the Sea of Marmara region to formulate reliable seismic hazard scenarios.

Finite-difference numerical analysis of faulting and accompanying seismicity near the Chuya and Kurai depressions, Gorny Altai, Russia

Numerical modeling of fault zone evolution and related seismicity can provide an insight into the process of large earthquake occurrences in a complicated fault system. In this paper, we develop a three-dimensional finite-difference numerical model of stress-strain evolution in and around the Chuya and Kurai depressions of Gorny Altai, Russia, to understand the fault zone evolution and the observed distribution of earthquakes in the region. Unlike in previous studies, the process of seismo-tectonic deformations of this region is addressed in a three-dimensional formulation with an improved model of rock massif behavior. A new geometrical model is designed, which is based on the seismotectonic, paleoseismological studies, and high-resolution Space-Radar-Topography-Mission data. The mathematical model applied here represents a set of partial differential equations, which are based on the fundamental conservation laws and constitutive equations for elastic and inelastic deformations. The initial stress state of the model is due to the action of gravity forces. The model is activated by assigning different displacement fields at the model boundaries – strike-slip and GPS-based displacements. The modeling results illustrate the stages of fault zone development and are in satisfactory agreement with the field observations in the case of GPS-based boundary conditions, which has not been modeled yet. Modeled seismic process is associated with the development of a fault zone resulting from the loss of strength in the subsurface points where the inelastic strain exceeds a certain threshold. The areas of high-degree of inelastic strain localization and the modeled fault zone represent an en-echelon system of dextral strike slips and various types of shear bands. The modeled seismic process obeys the Gutenberg-Richter (frequency-magnitude) law. The number of earthquakes in the attenuation part of the rock massif fracture process follows the Omori (aftershock decay) law.

Practice of Detailed Seismic Zoning of the Northwest Caucasus Taking into Account the Results of Paleoseismological Studies

A new generalization of Northwest Caucasus seismic hazard data is presented taking into account the influence of paleoseismological studies on the seismic hazard level. An attempt has been made to use data on paleoearthquakes for direct seismic hazard assessment by comparing, in accordance with the recurrence law, the magnitude of a strong earthquake with the estimated number of weak seismic events. A fundamentally new seismotectonic base (map of possible earthquakes source (PES) zones) has been prepared for compiling detailed seismic hazard maps of the region. Based on the map of PES zones, seismic impacts are calculated on a probabilistic basis. On the compiled maps, the northwestern and central segments of the Greater Caucasus look like a seismic hazardous area, where the level of seismic effects reaches 8.5 points on maps A and B. At the same time, compared to data from GSZ-97 maps, the results look more differentiated and overall appreciable decrease the level of seismic hazard in the region. The work is important from a methodological aspect in light of seismic risk management of this densely populated and actively developed Russian territory.

Use of small unmanned aerial vehicle (sUAV)-acquired topography for identifying and characterizing active normal faults along the Seerteng Shan, North China

High-resolution topographic datasets are being increasingly applied in studies of active tectonics for precise quantification of lateral and vertical offsets of landforms. Digital elevation models (DEM) acquired by airborne light detection and ranging (LiDAR) have also been used for morphological analysis of tectonic scarps to infer the seismic-slip history of active faults. However, the high cost of conducting LiDAR studies limits its widespread application. In contrast, the potential applicability of the low-cost and portable small unmanned aerial vehicles (sUAV) combined with structure-from-motion (SfM) techniques to investigate morphological features of fault-generated scarps and their paleoseismic implications has not been fully explored. Here, based on sUAV-acquired DEMs and field observations, we present a case study of the morphological features of fault scarps along the Seertengshan Piedmont Fault (SPF), a major boundary fault of the Hetao Graben, North China, and discuss their paleoseismic implications. The results demonstrate that low-angle (<25°) scarp slopes along the SPF suggestive of a long period of erosion are consistent with the results of paleoseismological studies (i.e., the most recent surface-faulting event occurred >2000 years ago). The observed 1.8–2.5-m-high fault scarps with single slope sections probably represent the most recent incremental displacements associated with surface-rupturing earthquake(s). Topographic data acquired by sUAV are suitable for quantitative morphological analyses of fault-generated scarps in actively deforming regions and can contribute to assessments of seismic hazard.

Quantifying rates of “rifting while drifting” in the southern Gulf of California: The role of the southern Baja California microplate and its eastern boundary zone

AbstractThe southern Baja California (Mexico) microplate has been rapidly moving away from the North America plate since ca. 12 Ma. This relative motion toward the northwest developed an oblique-divergent plate boundary that formed the Gulf of California. The rift-drift hypothesis postulates that when a continent ruptures and seafloor spreading commences, rifting on the plate margins ceases, and the margins start to drift, subside, and accumulate postrift sediments, eventually becoming a passive margin. In contrast to this hypothesis, the southern part of the Baja California microplate (BCM), and in particular its actively deforming eastern boundary zone, has continued significant rifting for millions of years after seafloor spreading initiated within the southern Gulf of California at 6–2.5 Ma. This is a process we call “rifting-while-drifting.” Global positioning system (GPS)–based data collected from 1998 to 2011 show relative motion across the eastern boundary zone up to ∼2–3.2 mm/yr with respect to a stable BCM. Furthermore, the velocity directions are compatible with normal faulting across the eastern boundary zone nearly perpendicular to the trend of the plate boundary at the latitude of La Paz and therefore a highly strain partitioned domain. North of 25°N latitude up to the Loreto area, there is a domain with no strain partitioning, and northwest-directed transtensional deformation dominates. From long-term geologic and paleoseismology studies, late Quaternary faulting rates are equal to or less than the GPS-derived rates, while geologic rates older than 1–2 Ma are commonly much higher. We suggest that the “rifting-while-drifting” process may be caused by the large topographic relief across the BCM margin, which created a significant gradient in gravitational potential energy that helps in driving continued relatively slow faulting. The relief was inherited from the much faster faulting of the BCM eastern boundary zone before plate motions largely localized along the modern transform–spreading centers in the axis of the Gulf of California. The low sediment flux from the small drainages and arid climate on the southern Baja California Peninsula result in the maintenance of underfilled to starved basins, and the relatively slow late Quaternary active faulting promotes continued topographic relief over millions of years.

Seismotectonics of Malatya Fault, Eastern Turkey

AbstractTurkey is located in a seismically active region with a complex tectonic history. In order to perform seismic risk assessment precisely, major fault zones (North Anatolian Fault Zone and East Anatolian Fault Zone) that are well defined are monitored continuously. It is a widely known fact that intraplate settings, such as Anatolian Plate, in which devastating earthquakes may occur, need to be observed densely. In this study, we investigate the seismotectonics of Malatya Fault within the Malatya Ovacık Fault Zone (MOFZ), which is one of the major agents responsible for internal deformation acting on Anatolian Plate. Recent geological and paleoseismological studies underline the necessity of comprehending the seismicity and latency of a major earthquake in this fault zone.We applied traditional techniques to investigate data of such a region. Earthquakes that occured in the vicinity of Malatya Fault between the years 2011 and mid-2019 are employed in a detailed analysis. The results of this study are constrained by the distribution of sensor networks in the region, yet allowing to define an active structure which is not included in the active fault map of Turkey, therefore, making a significant contribution to seismic hazard estimation.

Determination of stress distribution on active fault by means of Casagrande method; an innovative approach

The investigation deals with the stress distributions of undisturbed soil samples taken by preconsolidation press method from paleoseismological studies in the Gerede (Bolu) segment of the North Anatolian Fault System (NAFS), which is one of the most important intra-continental active transform faults in the world. Taking into consideration of the theoretical principal stress directions causing the faulting in the soil samples, consolidation experiments were carried out in different directions and the preconsolidation pressure values (PPV) of the samples were found by Casagrande method. Relations between the prime stress directions which are effective in the mechanism of fault formation and the values of PPV found by the Casagrande method were revealed. With all these calculations, the principal directions and magnitudes of the principal stresses causing faulting in the near-surface depths on the Gerede segment of the NAFS have been determined by a new method. The Gerede segment of the maximum principal stress (σ1) value at N 55.50 W and N 600 W was found 554.08 kPa and 327.54 kPa respectively. The maximum principal stress (σ1) direction of the fault was found to be N 55.50 W and the angle value was 44.50.

Paleoliquefaction Studies and the Evaluation of Seismic Hazard

Recent and historical studies of earthquake-induced liquefaction, as well as paleoliquefaction studies, demonstrate the potential usefulness of liquefaction data in the assessment of the earthquake potential of seismic sources. Paleoliquefaction studies, along with other paleoseismology studies, supplement historical and instrumental seismicity and provide information about the long-term behavior of earthquake sources. Paleoliquefaction studies focus on soft-sediment deformation features, including sand blows and sand dikes, which result from strong ground shaking. Most paleoliquefaction studies have been conducted in intraplate geologic settings, but a few such studies have been carried out in interplate settings. Paleoliquefaction studies provide information about timing, location, magnitude, and recurrence of large paleoearthquakes, particularly those with moment magnitude, M, greater than 6 during the past 50,000 years. This review paper presents background information on earthquake-induced liquefaction and resulting soft-sediment deformation features that may be preserved in the geologic record, best practices used in paleoliquefaction studies, and application of paleoliquefaction data in earthquake source characterization. The paper concludes with two examples of regional paleoliquefaction studies—in the Charleston seismic zone and the New Madrid seismic zone in the southeastern and central United States, respectively—which contributed to seismic source models used in earthquake hazard assessment.

Are U‐Th Dates Correlated With Historical Records of Earthquakes? Constraints From Coseismic Carbonate Veins Within the North Anatolian Fault Zone

AbstractU‐Th dating of carbonate veins in connection with active tectonics has recently been used as an attractive tool for constraining the absolute timing of late Quaternary crustal deformations. In this study, for the first time we correlate U‐Th ages of travertine deposits in coseismic fissures along the North Anatolian Fault Zone with records of paleoseismological studies supported by historical earthquake catalogued data. U‐Th ages are assessed in relation to the recurrence interval and the size and epicenter distance of major Holocene earthquakes. Our statistical evaluations on age correlations indicate that the carbonate vein precipitation is concentrated in eight different periods along the North Anatolian Fault Zone. The periods are well correlated with historical earthquake records and with previous dating results of the nearby trench studies. At least six of the periods correspond to the earthquakes reported in the historical catalogues. The age correlations of carbonate precipitation intervals for the last millennium show a recurrence along the eastern North Anatolian Fault Zone with a mode at 130–330 years that is consistent with a previously proposed paleoseismic recurrence interval of the fault. Recorded events in carbonate veins indicate a close‐epicenter (d &lt; 200 km) and high‐intensity (I &gt; VI) paleoearthquakes. Our results suggest that coseismic carbonate veins could be used to determine paleoseismic records as a supplementary tool to augment paleoseismological techniques. This tool has advantages over traditional paleoseismological methods for the understanding of long‐term earthquake behavior, particularly for prehistoric late Pleistocene events which cannot be dated easily by traditional paleoseismological methods.

Morphotectonic and paleoseismological studies of Late Holocene deformation along the Primorsky Fault, Baikal Rift

The Baikal Rift is the largest Cenozoic continental rift in Asia and has developed at the boundary between the Siberian craton and a collage of microplates composing the Amurian lithospheric plate. GPS data show that the Amurian plate moves southeastward at a rate of 3–4 mm/yr with respect to stable Eurasia but the slip rates along the main faults that control the opening of basins within the Baikal Rift System, are still poorly quantified. The recent graben system of the Olkhon region of the central Baikal Rift is a key example for studying of synrift faulting. We discovered a previously unknown paleoseismic structure in the course of our morphometric study of the Primorsky fault scarp, one of the youngest grabens within the Baikal Rift. Detailed topographic mapping of the deformation area and trenching across the fault scarp revealed two paleoseismic events responsible for scarp formation. Dating of organic remnants found in the trench walls allowed us to estimate a late Holocene age for the paleoearthquakes and bracket the vertical slip rates along the Primorsky Fault to between 0.5 ± 0.1 mm/yr (min) and 0.9 ± 0.2 mm/yr (max) over the last ~2.5 kyr. The geomorphological and paleoseismological data, in combination with the analysis of recent seismicity and horizontal geodetic rates, suggest that the Primorsky Fault has accumulated elastic stress with the potential for a ~M 6.6 earthquake. Large earthquakes of this magnitude have occurred at least twice on the investigated fault segment during the last ~1.4 kyr.

Physical constraints on speleothem deformations caused by earthquakes, seen from a new perspective: Implications for paleoseismology

Fractured speleothems, important earthquake environmental effects used in paleoseismological studies worldwide, are particularly effective for dating. Here, we discuss physical phenomena that can damage caves. We supplement the discussion with information (frequency characteristics and ground-motion parameters) from areas of mine openings threatened by induced seismicity, as analogs of cave conduits, as both, from a physical point of view, are underground voids affected by oscillations. Theoretical considerations indicate the use of bulk (P-wave) and shear (S-wave) moduli instead of Young's modulus, depending on the type of seismic wave affecting a given speleothem. Application of P-wave and shear moduli enables the calculation of a speleothem's natural frequency, based on measured P- and S-wave velocities as well as on the height and diameter of the speleothem. The relationship between the natural frequency, the acceleration causing speleothem failure, and the height and diameter of speleothems has been determined. Moreover, this acceleration value was compared to expected PGA values in order to find similarities between the two acceleration values. We highlight a phenomenon not previously considered in relation to cave environments, i.e., tunnel waves, which can appear in cave walls. This effect significantly changes oscillation characteristics in a cave, which can result in damage to speleothems which had not been expected to fail. Finally, we present the potential for estimating the minimum magnitude required to damage a cave at a given distance from its source.