Paleoseismological Investigations Research Articles

Tectonic-Paleoseismological Characteristics and Quaternary Activity of Maymundağı Fault (Northern Acıgöl Graben)

The Aegean region and its graben system constitute one of Turkey’s most significant seismic zones. The faults within the Aegean graben generate numerous earthquakes, leading to various human and economic losses. To better understand the seismicity of western Anatolia, it is necessary to obtain concrete findings regarding the seismic history of earthquake-producing graben faults. This can be achieved through paleoseismological studies and other relevant disciplines. This study focuses on paleoseismological investigations along the northern boundary fault of the Acıgöl graben, located east of the Aegean graben system. The Maymundağı fault zone has been examined in two separate segments: east and west. The Dazkırı segment to the east shows evidence of movement dating back at least 10,000 years, with subsequent intensified activity observed later on the western Bozkurt segment. An earthquake occurred approximately 2370 years ago east of the Bozkurt segment, followed by movements migrating westward, resulting in earthquakes approximately 1322 and 598 years ago. Further analysis of the western segment indicates an average recurrence interval of 724 years for earthquakes, with a slip rate of 0.58 mm/year. Based on these findings, a future earthquake can be expected in this region around 2028–2129 AD.

About the “predecessors” of the 2023 February earthquakes, Turkey

In the frame of a comprehensive investigation of historical earthquakes of Anatolia, we propose a re-appraisal of four major earthquakes/sequences occurred after 1000 AD (1114/1115, 1269, 1513/1514 and 1544), which could be considered as predecessors of the earthquakes of February 6, 2023. The main purpose is to provide reliable parameter values for the investigated earthquakes. Our investigation consisted of: retrieving and analysing the main primary historical sources; identifying the localities mentioned and assessing macroseismic intensity; determining earthquake parameters (location, magnitude and – where possible – the source azimuth) with the repeatable and transparent “Boxer” method, after properly calibrating the relevant coefficient by considering recent earthquakes of the Anatolian region. Our investigations show that the 1114 earthquake can be considered as a predecessor of the main 2023 earthquake, although the latter ruptured a larger area; the earthquake of 1544 may be a predecessor of the second event of 2023, February; and that the background of the 1513/1514 earthquake is so poor that a lot of care is required while handling the currently available parameters. In conclusion, we also compare our results with the findings of paleoseismological investigation and discuss how they contribute to understanding the rupture history of the East Anatolian Fault.

Tectonic geomorphology and paleoseismology of the Angelochori fault segment of the Anthemountas extensional detachment fault, Central Macedonia, Greece: Paleoseismic evidence from the 1677 CE earthquake

This study presents the results of a geomorphological and paleoseismological investigation on the Angelochori normal fault. This fault controls the southern boundary of the Anthemountas basin and constitutes the western segment of the Anthemountas extensional detachment fault (AEDF), a ∼48 km-long, E-W-trending, north-dipping low-angle normal fault in Central Macedonia, Greece. To assess the relative tectonic activity of the Angelochori fault and to determine the number, timing, and displacement of surface-faulting earthquakes, we conducted detailed field mapping and paleoseismological investigations. Our approach involved utilizing geomorphic indices, analyzing stratigraphic and structural relations, considering luminescence ages, and employing OxCal modeling techniques. The acquired data reveal, for the first time, the Middle-Late Holocene activity of the Anghelochori fault, providing constraints on the age of three strong (M > 6) surface-rupturing earthquakes over the last ∼7.7 ka. The youngest of these events aligns with the historical earthquake of the Anthemountas basin in 1677 CE. The observed minimum displacement per event ranges from 0.48 m to 0.65 m, consistent with a fault length estimated at about 24–28 km, suggesting an earthquake magnitude on the order of 6.6. The cumulative slip rate over the recorded period averages 0.21 ± 0.02 mm/a, with an average open recurrence interval of 2.6 ± 0.2 ka. Nonetheless, the displacement pattern displays alternating intervals of rapid slip at 0.60 ± 0.16 mm/a and slower slip at 0.08 ± 0.01 mm/a. Classified as Class 1, the Angelochori fault signifies an active tectonic structure posing a significant seismic hazard for the Thessaloniki metropolitan area.

Paleoseismological evidence for segmentation of the Main Himalayan Thrust in the Darjeeling-Sikkim Himalaya

Whether the Main Himalayan Thrust can host a single surface-rupturing event in the Himalaya with a rupture length of > 700 km remains controversial. Previous paleoseismological studies in the Darjeeling-Sikkim Himalaya (DSH) suggested medieval surface-rupturing earthquakes, correlating them with the eleventh–thirteenth century events from Nepal and Bhutan and extending the coseismic rupture length > 700 km. Conversely, there is no rupture evidence of the 1714 Bhutan and 1934 Bihar–Nepal earthquakes in the DSH, resulting in a discrepancy in the rupture extent of the great earthquakes. Consequently, we conducted a paleoseismological investigation across a ~ 10 m-high fault scarp on the Himalayan Frontal Thrust at Chenga village, DSH, revealing a surface-faulting event during 1313–395 BCE. We suggest that the DSH is a 150 km-long independent segment bounded by a transverse ridge and fault and has a recurrence interval of ~ 949–1963 years, which is significantly larger than Nepal (~ 700–900 years) and Bhutan Himalaya (~ 339–761 years).

Paleoseismological investigation along the back thrust bounding the northern limb of Janauri Anticline, NW Himalaya, India

Regardless of numerous paleoseismological studies along the active front of the Himalayas, it still lacks precision with respect to earthquake recurrence, rupture, slip mechanism, etc. which hinders understanding of the region's seismic hazards. Considering the seismic hazard posed by the previous Himalayan earthquakes, for instance, from Kashmir, Chamba, Kumaun-Garhwal, Nepal, etc., it becomes vital to identify the seismogenic structures and length of rupture that might be affected in the near future. In the present study, the paleoseismological investigation is carried out along the ∼150 km long Back Thrust (BT) of Himalayan Frontal Thrust bounding the northern limb of Janauri Anticline (JA) in northwest frontal Himalaya. By taking advantage of the optically stimulated luminescence (OSL) dating technique, the present study reports three newly identified seismic events along the BT i.e. 535-1269 AD Event I, 1447–1636 AD Event II, and 1660–1929 AD Event III. Our findings at Palahta locality of Punjab state complement, i.e., 1447–1636 AD (Event II), the effectiveness of previously identified more recent earthquake (MRE) at Hajipur, which further suggest the rupture length of ∼97 km along BT. The other results on the timing of seismic events (Event I and Event III) are well thought out and considered here as independent. Such independent events tend to fill an important gap in the database and provide us an opportunity to explore the paleoseismic events in more detail along the seismogenic structures of the Himalayas. Such a well-established database would assist in better seismic hazard estimation and will directly influence the long-term planning for infrastructure development in the regions like the Himalayas.

Correlation of paleoearthquake records at multiple sites along the southern Yangsan Fault, Korea: Insights into rupture scenarios of intraplate strike-slip earthquakes

The construction of spatiotemporal models of earthquake occurrence for intraplate areas is challenging due to the low deformation rates in these areas. In this study, we conducted paleoseismological investigations along the southern Yangsan Fault (SYF), a typical low-deformation-rate fault, on the Korean Peninsula. The SYF is distinct from the northern Yangsan Fault (NYF), and the boundary between them is located at the junction between the NNE-striking YF and another major structure, the NNW-striking Ulsan Fault (UF), which branches off from the YF. Paleoseismological trenches at four sites along the SYF indicate that this fault section has not ruptured during the Holocene, in contrast to the NYF and UF. In detail, surface ruptures along the studied section of the SYF occurred during three different time periods, as inferred from stratigraphy and radiocarbon dating: 74 to 49 ka at two sites, 39 to 35 ka at another site, and 28,000 cal yr BP (or 30 ka considering the OSL age) to 16 ka at all sites. These results suggest two alternative rupture scenarios for the timing of paleoearthquakes along the studied fault section during the Late Pleistocene: (1) full rupture along the entire studied section during each earthquake event, or (2) multiple partial ruptures along the two structurally distinguishable parts of the studied fault section, that is, the Wolsan–Miho and Inbo north–Inbo sections. We conclude that geometric discontinuities of the long-lived YF system in the Korean Peninsula intraplate region have played an important role in controlling recent spatiotemporal rupture behavior.

Paleoseismology of the Sürgü and Çardak faults - splays of the Eastern Anatolian Fault Zone, Türkiye

The sinistral East Anatolian Fault Zone (EAFZ) and the dextral North Anatolian Fault Zone (NAFZ) are two important strike-slip faults that delimit the boundaries of the Anatolian plate. The north-south directed compressional forces in eastern Türkiye trigger the westward escape of the Anatolian plate along these prominent structures. This study aims to reveal the earthquake history of the Sürgü and Çardak faults, which are important fault segments that splay from the EAFZ. In this context, overall, four paleoseismologic trenches were dug, two trenches on the Sürgü Fault and two trenches on the Çardak Fault. Along the Sürgü Fault, at least two paleoearthquake events have been determined on the trench walls, one event occurred around 3400 BCE and the second event happened between 2085 ± 65 BCE and 790 ± 20 BCE. Moreover, trenching results from the Çardak Fault indicate two surface rupturing paleoearthquakes between 10520 ± 95 BCE and 5780 ± 65 BCE, and between 3215 ± 125 BCE and 825 ± 55 CE, respectively. The focal mechanisms of important instrumental earthquakes around the Sürgü and Çardak faults on the EAFZ show that NNE-SSW trending compressional forces are actively dominating the tectonic setting of the region in the contemporary era. Paleoseismological investigations suggested that the Sürgü and Çardak faults have the potential to produce surface-rupturing earthquakes with an estimated magnitude of 7 or larger.

Paleoseismological Investigations in the Chikoy Fault Zone (Southern Transbaikalia)

Paleoseismological Investigations in the Chikoy Fault Zone (Southern Transbaikalia)

Estimating the long-term slip rate of active normal faults: The case of the Paganica Fault (Central Apennines, Italy)

The footwall of the surface rupturing Paganica normal fault, the source of the 2009 L’Aquila earthquake (Mw 6.1) in the Central Apennines (Italy), was investigated using integrated geological and geomorphological approaches. The aim was to constrain the active tectonics by studying the Raiale River that orthogonally crosscuts the fault trace, where it provides a useful geomorphological marker of long-term fluvial incision and footwall uplift. Using morphostratigraphy and paleomagnetic analysis, the Plio–Pleistocene morphotectonic evolution of the area was reconstructed, comprising an ancient continental basin and paleolandforms that predate the footwall incision. Starting from the Late Early Pleistocene–Middle Pleistocene, fluvial dissection was mainly due to marked river downcutting triggered by significant activity of the Paganica Fault, which caused progressive base-level lowering. The Raiale River downcutting formed five Middle–Late Pleistocene fluvial terraces, that, along with absolute Optically Stimulated Luminescence (OSL) dating, allowed the identification of paleolongitudinal profiles with a diverging downstream configuration. Terrace dating yielded a minimum incision rate of 0.25 ± 0.02 mm/a, which only partially compensates the footwall uplift and can thus be considered as a minimum value for the Paganica Fault throw rate, which could reach up to ~0.45 mm/a. In parallel, using terrestrial cosmogenic nuclides, a denudation rate of 0.02–0.04 mm/a was measured on the summit of the footwall block. This denudation is in keeping with the drainage incision, suggesting a non-steady state for the fault footwall topography and a dominance of relief growth. Last, the analysis of the modern Raiale River longitudinal profile denoted an ungraded status, with two main knickzones that we interpret as transient forms due to tectonic perturbations, likely triggered by activity of the Paganica Fault during the end Early Pleistocene and the Late Pleistocene. Considering the 2009 L’Aquila earthquake coseismic rupture, we observe that the younger transience on the Raiale River longitudinal profile, if it is of tectonic origin, could have only been produced by much larger seismic events (i.e., Mw > 6.5) than those documented in the area by paleoseismological investigations. The collective results confirmed that in the Central Apennines, conditions of dynamic equilibrium are often not met, and that the persistence of transient perturbations induced by tectonics should be accounted for.

A Probabilistic Physics-Based Seismic Hazard Model for the Alborz Region, Iran

ABSTRACTThe seismic activity rate is one of the most significant factors in seismic hazard modeling. Although it is usually estimated from observed seismicity, a complete picture of the possible earthquakes is not always available since catalogs of the observed earthquakes are short and incomplete. Long-term physics-based numerical simulations, providing a comprehensive range of earthquakes, are a decent way to overcome such deficiency. With this contribution, we built a seismic hazard model for the Alborz region, Iran, using a long-term physics-based synthetic earthquake catalog, enriched with the additional consideration of background seismicity derived from a deformation model. 200,000 yr synthetic catalogs for the Alborz region, Iran, are used and validated by considering the recurrence time of large-magnitude events estimated from the paleoseismological investigation on individual faults. The magnitude–frequency distribution (MFD) from the synthetic earthquake catalog is then compared with the MFD based on observation, which overall indicates good compatibility, although there are discrepancies for some faults. The estimated peak ground acceleration (PGA) for the Alborz region varies in the ranges of 0.16–0.52g and 0.27–1.0g for 10% and 2% probability of exceedance in 50 yr, respectively. The absolute natural logarithm differences averaged across the region are ∼0.21, corresponding to an average of 23% difference in PGA values in comparison with the most up-to-date observed-based hazard model. Hazard curves for several populated cities are also presented and compared with the other independent estimates. The proposed procedure could be an alternative approach to evaluate seismic hazard for a seismically active region, in particular for those without a complete catalog of observed earthquakes.

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.

The 2019 Le Teil surface-rupturing earthquake along the La Rouvière Fault within the Cévennes fault system (France): What does paleoseismology reveal?

The 2019-11-1, Mw4.9 Le Teil earthquake occurred within the NE termination of the Cévennes faults system (CFS) in southern France, along the La Rouvière fault (LRF), an Oligocene normal fault which was not known to be potentially active. This shallow moderate magnitude reversefaulting event produced a 5 km-long surface rupture and strong ground shaking. No evidence of previous quaternary activity was observed in the morphology, raising the question whether the fault had been reactivated for the first time since the Oligocene or had broken the surface in the past without being detected in the morphology. To address this issue, we carried out paleoseismological investigations to analyze and characterize evidences of paleo-ruptures in Quaternary deposits. We discovered that at least one event prior 2019, occurred between 13.5 and 3.3 ka within the central part of the fault segment that broke in 2019, and that a possible earlier surfacerupturing event occurred within the northern part of this segment during the 16th century. Further investigations coupling sub-surface geophysical investigations and trenching are now carried out within the southern and northern segments of the LRF as well as along the other fault segments of the CFS.

Paleoseismological evidence for historical ruptures along the Meduno Thrust (eastern Southern Alps, NE Italy).

We carried out new geological, morphotectonic, geophysical and paleoseismological investigations on the Meduno Thrust that belongs to the Pliocene-Quaternary front of the eastern Southern Alps in Friuli (NE Italy). The study area is located in the Carnic Prealps, where a series of alluvial terraces, linked to both climatic and tectonic pulses characterises the lower reach of the Meduna Valley. In correspondence of the oblique ramp of the Meduno Thrust, the Late Pleistocene Rivalunga terrace shows a set of scarps perpendicular to the Meduno valley, often modified by human activity. In order to reconstruct the tectonic setting of the area and identify the location for digging paleoseismological trenches, integrated geophysical investigations including electrical resistivity tomography, seismic refraction and reflection, ground penetrating radar and surface wave analyses (HVSR, ReMi and MASW), were carried out across the scarps of the Rivalunga terrace. Geophysical surveys pinpointed that in correspondence of the oblique ramp, stress is accommodated by a transpressive thrust system involving all the seismo-stratigraphic horizons apart from the ploughed soil. Trenching illustrated the Meduno Thrust movements during Late Pleistocene-Holocene. Trenches exhibited both shear planes and extrados fracturing, showing deformed alluvial and colluvial units. 14C datings of the colluvial units show that the most recent fault movements occurred after 1360 CE and 1670 CE. The age of the deformed stratigraphic units compared with the earthquakes listed in current catalogues, suggests that the 1776 earthquake (Mw 5.8, Io = 8–9 MCS) could represent the last seismic event linked to the Meduno thrust activity. This study provided new quantitative constraints improving seismic hazard assessment for Carnic prealpine area.

Ground-Penetrating Radar Imaging of Near-Surface Deformation along the Songino Active Fault in the Vicinity of Ulaanbaatar, Mongolia

The seismic activity observed in the vicinity of Ulaanbaatar (UB) capital city has been increased since 2005. Several active faults have been identified in the UB area. Most of the Mongolian population is concentrated around UB (1.5 million), which is the main political and economic center of the country. Hence, the study of seismic hazard is of first importance for the country. In this paper, we present the GPR results obtained on the Songino fault which is situated at 20 km west-southwest of UB at the northeast tip of Khustai fault. The combination of the morphotectonic, GPR and paleoseismological investigations brings essential information for seismic hazards assessments. The 2D GPR profiles are measured by using 250 and 500 MHz antennae and the topography using a differential GPS. An appropriate processing of the GPR data, including the topographic migration, allows us to bring out indirect characteristics of these faults. The objective is to identify near-surface geometry and coseismic deformation along the mapped fault. The 250 MHz GPR images of the Songino fault show the evolution of the sub-surface deformation mode induced by the arched geometry of the Songino fault. We observe a clear compressive structure at its NW section, strike slip at its central section and extensive structure in its SE part.

Geophysical evi-dence of the 1912 earthquake rupture along the central fault system of the Acambay Graben, Central Mexico

In this work, we have applied two geophysical techniques in two different areas of potential interest for paleoseismological assessment of the active faults of the Acambay graben. The main goal was to localize segments of buried faults suspected to break the surface during the 1912 Acambay Earthquake, in order to (1) identify favorable sites for paleoseismological investigation purpose and (2) extrapolate the data obtained with a paleoseismic trenching. On the one hand, Electromagnetic Induction (EMI) Method was used to map the horizontal variation of the apparent resistivity in order to detect the 1912 surface rupture of the Temascalcingo fault in the alluvial plain of the Lerma River. On the other hand, within a volcanic edifice, the Electrical Resistivity Tomography (ERT) tech-nique was used to characterize the electrical resistivity distribution along a profile in or-der to detect and localize the San Pedro fault, partially buried in a Holocene sedimentary filling of a small endorheic basin. Results of these studies allow defining location and orientation of the structures that potentially broke the surface during the 1912 earthquake and are partially hidden by recent deposits filling the tectonic depressions. Good correla-tion between ERT subsurface to deep imagery of faults and a trench survey which cuts across the San Pedro fault trace, illustrate the pertinence to use such techniques for pale-oseismological investigation purpose in volcano-sedimentary environments.

Fissure Ridges: A Reappraisal of Faulting and Travertine Deposition (Travitonics)

The mechanical discontinuities in the upper crust (i.e., faults and related fractures) lead to the uprising of geothermal fluids to the Earth’s surface. If fluids are enriched in Ca2+ and HCO3-, masses of CaCO3 (i.e., travertine deposits) can form mainly due to the CO2 leakage from the thermal waters. Among other things, fissure-ridge-type deposits are peculiar travertine bodies made of bedded carbonate that gently to steeply dip away from the apical part where a central fissure is located, corresponding to the fracture trace intersecting the substratum; these morpho-tectonic features are the most useful deposits for tectonic and paleoseismological investigation, as their development is contemporaneous with the activity of faults leading to the enhancement of permeability that serves to guarantee the circulation of fluids and their emergence. Therefore, the fissure ridge architecture sheds light on the interplay among fault activity, travertine deposition, and ridge evolution, providing key geo-chronologic constraints due to the fact that travertine can be dated by different radiometric methods. In recent years, studies dealing with travertine fissure ridges have been considerably improved to provide a large amount of information. In this paper, we report the state of the art of knowledge on this topic refining the literature data as well as adding original data, mainly focusing on the fissure ridge morphology, internal architecture, depositional facies, growth mechanisms, tectonic setting in which the fissure ridges develop, and advantages of using the fissure ridges for neotectonic and seismotectonic studies.

Interactions between active tectonics and gravitational deformation along the Billecocha fault system (Northern Ecuador): Insights from morphological and paleoseismological investigations

The Billecocha plateau (4000 m a.s.l.) lies in the high elevation Ecuadorian Andes volcanic arc. It overhangs by 2000 m above the interandean valley. Both the plateau and surrounding volcanoes are heavily affected by active faulting characterized by straight, sharp and discontinuous scarps within a 6 km wide and 24 km long corridor. Contrasting interpretations have been proposed to explain the expression at surface of the so-called Billecocha fault system (BFS), from normal faulting related to postglacial elastic rebound or gravitational processes, to right-lateral faulting compatible with the North-Andean Sliver tectonic regime. The instrumental seismicity recorded around the BFS is low, however, a M~7 earthquake heavily struck the region in 1868.With the aim to discuss the kinematic and coseismic nature of the encountered deformations as well as the seismogenic character of the BFS, we performed (1) morphological analysis to map and quantify evidence of active faulting and (2) paleoseismological investigations across the longer segment of the fault system. In three trenches, we show that surface deformations are at least partly coseismic in origin during the Holocene with a minor lateral component, the last paleoseismic event being compatible in date with the 1868 earthquake. In addition, some of the enlightened paleoseismic events could have occurred in relationship with volcanic eruptions of the surrounding volcanoes.While field evidence of reverse and strike slip faulting suggests that regional tectonics could be involved, the geomorphological signature of the BFS at the mountain scale, as seen on the digital surface model, can partly be related to the development of deep seated gravitational deformations, hence suggesting an interaction between boundary (i.e. tectonic, volcanic) and body forces (i.e. gravity, post-glacial rebound). Further studies are however mandatory to better address the influence of each process at the BFS, in particular geodetic and seismological surveys.Given the available data, we suggest that the BFS could actually correspond to the distributed surface expression of the tectonic reactivation of the inherited Pujilí suture, enhanced by gravitational phenomenon. In this light, paleoearthquakes identified along the BFS may help evidencing the recurrence of major events in the region. However, it also imply that surface deformations along the BFS shall not be used without a careful and more detailed field work to derive fault slip rates for seismic hazard calculations.

An update of Algerian’s seismic catalog from historical seismicity, archeoseismological, and paleoseismological studies

For any seismic hazard study, a reliable, homogenized, and complete seismic catalog is required. The Algerian seismicity catalog has been recently updated by retrieving and reappraising many historical events. The Algerian seismic network has also been densified up to about 80 seismic stations covering the Tell Atlas which is the most active area of northern Algeria for monitoring of the seismic activity reducing the magnitude threshold. Recently, we have launched archeoseismological studies to retrieve past strong earthquakes that have affected Roman sites located along the Tell Atlas. Here, we proceed with tectonic investigations around selected sites where significant observed damage were identified. On the other hand, paleoseismological investigations were conducted along the El Asnam fault (now Chlef) following the large Ms 7.3 earthquake of 1980. Paleoseismic studies combined with archeoseismological results provide the dating of past earthquakes and contribute to the completeness of the seismicity catalog.

Paleoseismology of the western Sürgü–Misis fault system: East Anatolian Fault, Turkey

The East Anatolian fault bifurcates into a north strand and a south strand near the City of Celikhan, Turkey. The northern strand is referred to as the Surgu–Misis fault (SMF) system, which is divided into a number of distinct fault segments based on geological and geomorphological characteristics. However, no paleoseismological data regarding the movement history of the SMF system previously have been reported. We excavated seven trenches across four segments of the SMF system to evaluate the paleoseismological history of these fault zones. These trenches exposed structural and sedimentological evidence of paleoseismic events that had primarily strike-slip displacements with secondary normal and reverse components of motion. Geochronological dating of the trench stratigraphy and event horizons provide the time elapsed since the last event and confirmed the Holocene activity of the faults. These fault segments are individually capable of producing surface-rupturing earthquakes, but may also rupture together generating large, complex, multi–segment ruptures. However, the SMF system has not produced surface-rupturing earthquakes in the last millennia, and therefore is accumulating strain. In light of our findings, we suggest that about 1.7 m of strain has accumulated across the Karatas and Yumurtalik fault segments, which is sufficient to produce moderate to large earthquakes when released seismically. The surrounding Gulf of Iskenderun is a highly industrialized district in the Eastern Mediterranean. Therefore, the data obtained from this paleoseismological investigation will contribute to a better understanding of the earthquake hazards in the region.

Roman to Middle Age Earthquakes Sourced by the 1980 Irpinia Fault: Historical, Archaeoseismological, and Paleoseismological Hints

The Italian seismic compilations are among the most complete and back-in time extended worldwide, with earthquakes on record even before the Common Era. However, we have surely lost the memory of dozen strong events of the historical period, mostly in the first millennium CE. Given the lack of certain or conclusive written sources, besides paleoseismological investigations, a complementary way to infer the occurrence of lost earthquakes is to cross-check archaeoseismic evidence from ancient settlements. This usually happens by investigating collapses/restorations/reconstructions of buildings, the general re-organization of the urban texture, or even the abrupt abandonment of the settlement. Exceptionally, epigraphs mentioning more or less explicitly the effects of the earthquake strengthened the field working hypothesis. Here, I deal with both paleoseismological clues from the Monte Marzano Fault System (the structure responsible for the catastrophic, Mw 6.9 1980 earthquake) and archaeoseismological evidence of settlements founded in its surroundings to cast light on two poorly known earthquakes that occurred at the onset and at the end of the first millennium CE, likely in 62 and in 989 CE. Both should share the same seismogenic structure and the size of the 1980 event (Mw 6.9).