Long-term Slip Rate Research Articles

Interseismic fault slip deficit and coupling distributions on the Anninghe-Zemuhe-Daliangshan-Xiaojiang fault zone, southeastern Tibetan Plateau, based on GPS measurements

The Anninghe-Zemuhe-Daliangshan-Xiaojiang (AZDX) fault zone is an important boundary between the South China block and southeastern (SE) Tibetan Plateau. Its strong earthquake potential has been highly concerned, because remarkable left lateral strike-slip motion has been observed in this fault zone. Using the linear spherical block model constrained by a refined GPS horizontal velocity field, we have derived the detailed partial slip deficits and the coupling fraction distributions along the AZDX fault zone, as well as self-consistent long-term slip rates on major active faults in SE Tibetan Plateau. Our results identified three remarkable slip deficit regions with high fault coupling fractions (0.6–1.0), including the southern segment of the Anninghe Fault (north of Xichang), the southern segment of the Daliangshan Fault (Butuo-Qiaojia), and southern terminus of the Xiaojiang Fault. These regions spatially coincide with the seismic gaps inferred from the spatiotemporal distributions of historical earthquake ruptures and paleoearthquake surveys, jointly implying their higher strong earthquake potential. Furthermore, combining with analyses of GPS data, previous geological and numerical simulation studies, we tentatively discussed the possible effect range of the Burma arc tectonic domain.

Interseismic Slip and Coupling along the Haiyuan Fault Zone Constrained by InSAR and GPS Measurements

The Haiyuan fault zone is an important tectonic boundary and strong seismic activity belt in northeastern Tibet, but no major earthquake has occurred in the past ∼100 years, since the Haiyuan M8.5 event in 1920. The current state of strain accumulation and seismic potential along the fault zone have attracted significant attention. In this study, we obtained the interseismic deformation field along the Haiyuan fault zone using Envisat/ASAR data in the period 2003–2010, and inverted fault kinematic parameters including the long-term slip rate, locking degree and slip deficit distribution based on InSAR and GPS individually and jointly. The results show that there is near-surface creep in the Laohushan segment of about 19 km. The locking degree changes significantly along the strike with the western part reaching 17 km and the eastern part of 3–7 km. The long-term slip rate gradually decreases from west 4.7 mm/yr to east 2.0 mm/yr. As such, there is large strain accumulation along the western part of the fault and shallow creep along the Laohushan segment; while in the eastern section, the degree of strain accumulation is low, which suggests the rupture segments of the 1920 earthquake may have been not completely relocked.

The life span of fault-crossing channels.

Successive earthquakes can drive landscape evolution. However, the mechanism and pace with which landscapes respond remain poorly understood. Offset channels in the Carrizo Plain, California, capture the fluvial response to lateral slip on the San Andreas Fault on millennial time scales. We developed and tested a model that quantifies competition between fault slip, which elongates channels, and aggradation, which causes channel infilling and, ultimately, abandonment. Validation of this model supports a transport-limited fluvial response and implies that measurements derived from present-day channel geometry are sufficient to quantify the rate of bedload transport relative to slip rate. Extension of the model identifies the threshold for which persistent change in transport capacity, obliquity in slip, or advected topography results in reorganization of the drainage network.

Reconstructing the slip velocities of the 1202 and 1759 CE earthquakes based on faulted archaeological structures at Tell Ateret, Dead Sea Fault

Archaeological structures built across active faults and ruptured by earthquakes have been used as markers to measure the amount of displacement caused by ground motion and thus to estimate the magnitude of ancient earthquakes. The example used in this study is the Crusader fortress at Tel Ateret (Vadum Iacob) in the Jordan Gorge, north of the Sea of Galilee, a site which has been ruptured repeatedly since the Iron Age. We use detailed laser scans and discrete element models of the fortification walls to deduce the slip velocity during the earthquake. Further, we test whether the in-situ observed deformation pattern of the walls allows quantification of the amount both sides of the fault moved and whether post-seismic creep contributed to total displacement. The dynamic simulation of the reaction of the fortification wall to a variety of earthquake scenarios supports the hypothesis that the wall was ruptured by two earthquakes in 1202 and 1759 CE. For the first time, we can estimate the slip velocity during the earthquakes to 3 and 1 m/s for the two events, attribute the main motion to the Arabian plate with a mostly locked Sinai plate, and exclude significant creep contribution to the observed displacements of 1.25 and 0.5 m, respectively. Considering a minimum long-term slip rate at the site of 2.6 mm/year, there is a deficit of at least 1.6 m slip corresponding to a potential future magnitude 7.5 earthquake; if we assume ~5 mm/year geodetic rate, the deficit is even larger.

Observation-constrained multicycle dynamic models of the Pingding Shan earthquake gate along the Altyn Tagh Fault

Earthquake gates are fault geometric complexities, common in natural fault systems, that conditionally impede earthquake ruptures. This study centers on modeling of multicycle dynamics of the Pingding Shan earthquake gate along the central Altyn Tagh Fault in northwest China. The earthquake gate includes three geometric complexities: a prominent restraining bend, a 4-km wide stepover to the east, and a releasing bend to the west. We use a 2D finite element method to simulate coseismic spontaneous ruptures with interseismic fault stress evolutions computed by an analytic viscoelastic solution. Paleoseismic records and long-term slip-rates are used to constrain the models. We find that fault-geometry-related heterogenous stresses accumulated over earthquake cycles yield complex rupture patterns and help explain earthquake recurrence intervals revealed by paleoseismic records. The three most important contributions to the heterogeneous stresses come from dynamic ruptures passing fault geometric complexities, fault-strike-dependent tectonic loading and relaxation, and stress history from past earthquakes. In the Pingding Shan earthquake gate, the releasing stepover appears to impede ruptures more effectively than the restraining bend. The combined impact of the restraining bend and the releasing stepover makes the Pingding Shan earthquake gate a very effective barrier to 350-km model-spanning ruptures. The best-fit model yields a low recurrence interval of 4.6 kyrs for 350-km-long ruptures, interspersed with more frequent ruptures limited to individual fault segments. A lower static friction tends to reduce the effectiveness of the earthquake gate to impede ruptures. Local fault geometric complexities together with rapid energy release and restrengthening of friction during dynamic ruptures help explain the 0.66 recurrence interval coefficient of variation (COV) recorded at the Copper Mine paleoseismic trench site on the Xorxoli segment. This study provides a method for applying heterogenous initial stresses for single-event dynamic rupture simulations that consider the effect of past earthquakes and fault geometry.

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.

Tectonic geomorphology and paleoseismology of the northern East Franklin Mountains fault, El Paso, Texas, USA

The 45 km-long, north-trending East Franklin Mountains Fault lies in the southern Rio Grande rift (Texas). Late Quaternary normal fault scarps up to 20 m high traverse the eastern range front, but also bulge up to 2 km out onto the piedmont in lobes as much as 3.5 km wide. In the lobe areas the range-front fault strand displays no fault scarps, as if displacement has shifted to the piedmont strand since ca. 400 ka. We divide the faulted piedmont alluvial fans into seven age classes (from Middle Pleistocene to Holocene), based on erosional dissection and soil profile development. Piedmont scarps in Qf1 deposits (250–400 ka) range from 18 to 20 m high; in Qf2-3 deposits (65–100 ka), 9–10 m high; and in Qf3-4 deposits (20 ka), 2.7–4 m high (the latest displacement event). Scarp heights underestimate true vertical displacement of the footwall surface, which lies buried beneath younger fan deposits of unknown thickness on the hanging wall. Hanging-wall aggradation also causes variable scarp heights along strike on single-age landforms, with burial thickness a second-degree polynomial function (parabolic) of distance to the nearest active stream. Our paleoseismic trench on a 9.8 m-high scarp exposed evidence for five displacement events in the past 44 ka, the latest three of which had vertical displacements of 3–4 m. Such displacements imply surface ruptures longer than the 26.5 km fault length previously mapped in the USA, indicating rupture extended onto adjacent faults. The minimum long-term slip rate (>11.2 m in 44 ka) is 0.25 mm/yr; over last full seismic cycle (ca. 11–29 ka) it is 0.20–0.21 mm/yr. Optically-stimulated luminescence (OSL) dating shows that fine sand-silt grains in colluvial deposits were not all zeroed during deposition. Single-aliquot dating of quartz grains yielded multiple OSL age peaks, the youngest peaks of which yield a chronology compatible with stratigraphy and soil development in the colluvial wedge sequence.

Active Fault Systems in the Inner Northwest Apennines, Italy: A Reappraisal One Century after the 1920 Mw ~6.5 Fivizzano Earthquake

Based on the review of the available stratigraphic, tectonic, morphological, geodetic, and seismological data, along with new structural observations, we present a reappraisal of the potential seismogenic faults and fault systems in the inner northwest Apennines, Italy, which was the site, one century ago, of the devastating Mw ~6.5, 1920 Fivizzano earthquake. Our updated fault catalog provides the fault locations, as well as the description of their architecture, large-scale segmentation, cumulative displacements, evidence for recent to present activity, and long-term slip rates. Our work documents that a dense network of active faults, and thus potential earthquake fault sources, exists in the region. We discuss the seismogenic potential of these faults, and propose a general tectonic scenario that might account for their development.

The tectono-stratigraphic evolution of the Fucino Basin (central Apennines, Italy): new insights from the geological mapping of its north-eastern margin.

ABSTRACT We present the geological map of the north-eastern margin of the Fucino Basin, which is mainly characterized by Plio-Quaternary continental deposits that show transition from deeper-water lacustrine environment, marginal lacustrine system, and fluvial facies. These deposits unconformably overlie upper Messinian Lago-Mare sediments and pre-orogenic carbonate succession. The occurrence of Caspiocypris tiberina in the Plio-Quaternary lacustrine sediments, coupled with the normal magnetic polarity of Casa Colombaia section, led to suggest the onset of the sedimentation of these continental deposits to the late Piacenzian (2.58–3.04 Ma). The upper Messinian deposits are characterized by ostracod assemblages related to the Loxocorniculina djafarovi zone, pointing to the last Lago-Mare event of the Messinian Salinity Crisis (5.40–5.33 Ma). This new stratigraphic framework may be useful to refine the long-term slip rates of the still active normal faults that affect the north-eastern margin of the Fucino Basin.

Late Quaternary sinistral strike-slipping of the Liupanshan-Baoji fault zone: Implications for the growth of the northeastern Tibetan Plateau

The Liupanshan-Baoji fault zone is one of the outermost parts of the northeastern Tibetan Plateau. Its fault behavior allows us to address one of the major questions in understanding the growth pattern of the northeastern Tibetan Plateau. Here, we present the strike-slip rates and the initiation times of two key active faults in the Liupanshan-Baoji fault zone: the East Liupanshan Fault (ELF) and Longxian-Qishan-Mazhao Fault (LQMF), to identify whether the NE Tibetan plateau grew outwards sequentially or deformed simultaneously. Based on the geomorphic marker offsets, fault ages constrained by the 14C dating, and previous studies, we first determine the average slip rates of 0.7–2.0 mm/a and 0.5–0.9 mm/a along the southernmost ELF and the LQMF. Then we estimate the total left-lateral displacements along the two faults, 4 km on the ELF and ~ 1 km on the LQMF. If the long-term slip rates on those two faults were constant during late Cenozoic time, the initiation dates of the sinistral movements would be ~3 Ma and ~ 1.4 Ma, concurrent with the changes in sediment accumulation and sizes around the nearby Cenozoic basins, as well as the development of river terraces in the northeastern Tibetan Plateau. We therefore infer that the kinematic behavior on the two faults is caused by the clockwise rotation of the Longxi Terrane. The results further highlight the two stages of tectonic deformation at 3 Ma and 1 Ma in the northeastern margin of the Tibetan Plateau.

Quantitative Estimate of the Long-Term Slip Rate of the Normal Fault Responsible for the 2009 L’Aquila Earthquake (Mw 6.1) (Central Italy) Through Tectonic Geomorphology Approaches

Quantitative Estimate of the Long-Term Slip Rate of the Normal Fault Responsible for the 2009 L’Aquila Earthquake (Mw 6.1) (Central Italy) Through Tectonic Geomorphology Approaches

Quantitative Estimate of the Long-Term Slip Rate of the Normal Fault Responsible for the 2009 L’Aquila Earthquake (Mw 6.1) (Central Italy) Through Tectonic Geomorphology Approaches

Quantitative Estimate of the Long-Term Slip Rate of the Normal Fault Responsible for the 2009 L’Aquila Earthquake (Mw 6.1) (Central Italy) Through Tectonic Geomorphology Approaches

Palaeoseismic behaviour of strike-slip faults in slowly deforming regions: palaeoearthquakes and long-term slip history of the Ovacık Fault (eastern Turkey)

The Ovacik Fault (OF) is one of the internal structures of the Anatolian Block, located close to its eastern boundary. Although it shows a very clear surface trace, there are no instrumentally recorded surface rupturing earthquakes on this fault. This study concludes results of the first palaeoseismological trench study on the OF with the evidence for three surface rupturing earthquakes for the last 6 kyr. Structural, stratigraphical and geochronological constraints show that the oldest event happened between 4700 and 3022 BCE, whereas the penultimate event was between 2262 and 1643 BCE. The youngest event happened after 56 BCE, which we could only delimit from below because of the absence of any dateable material from the upper layers of the relevant horizons. The derived mean interevent time of these three palaeoevents is 2400 ± 765 years. We could not correlate any of these palaeoevents with historical earthquakes due to the absence of records in catalogues for the region of interest. Moreover, we used cumulative offsets of the major drainages to calculate the long-term slip rate of 2.7 mm/year since the Pliocene, which exceeds slip rates of other internal faults of Anatolia almost by the factor of two. Our results do not only show significant deformation for the internal parts of Anatolia but also point out a seismic potential of the OF.

Growth Model and Tectonic Significance of the Guman Fold Along the Western Kunlun Mountain Front (Xinjiang, China) Derived From Terrace Deformation and Seismic Data

The activity of blind thrust faults drives fold deformation of overlying strata, leading the folds to be geometrically related to the underlying blind thrust faults. However, it is often challenging to select an appropriate kinematic model for a thrust fault-related fold. To construct the model of the Guman fold in front of the Western Kunlun Mountains in western China, we interpret deformed terrace profiles and a high-resolution seismic reflection profile that crosses the fold. Combining deformation characteristics of the terrace profiles and subsurface structures interpreted from the seismic reflection data, the Guman fold is best explained as a fault-bend fold with lower flat-ramp-upper flat geometry that grows by kink-band migration. Previous studies and the seismic reflection profile show that the blind fault ramp dips 20±4° to the south. Using the fault bend fold model with Monte Carlo probability distributions, the uplifted and dated T1c terrace surface (250±35 ka) and fault geometry indicate a slip rate of 2.6+1.3/-0.4 mm/yr along the underlying fault ramp. The uplift of the pre-growth strata across the underlying fault ramp combined with the fold initiation in the early Pleistocene (2.14–1.8 Ma) indicate a long-term slip rate of 1.7+0.6/-0.2 mm/yr along the underlying fault ramp. For a lower flat-ramp-upper flat fault-bend fold with fault dip of 20°, 13% of the slip along the underlying fault ramp would be absorbed by the fold above the fault ramp, whereas 87% of the slip will be transferred forward along the upper fault flat. Therefore, the shortening accommodated by the Guman anticline is 0.34+0.18/-0.06 mm/yr while the slip rate along the upper fault flat is 2.3+1.1/-0.4 mm/yr since the T1c terrace abandonment. This result explains why the shortening of the Guman Anticline is largely hidden from the relative movement of GPS sites to the north and south of the fold. These findings support the view that most of the crustal shortening of the West Kunlun Mountains is transferred basinward along the shallow detachment and is likely ultimately absorbed by the Mazartagh Thrust located 200 km away in the hinterland of the Tarim Basin.

Geomorphic and paleoseismological evidence of active Kachchh Mainland Fault, Kachchh, India

The present work pertains to the stratigraphic evidences found during paleoseismic investigations on the trench walls opened across the Kachchh Mainland Fault (KMF). High-resolution satellite (CARTOSAT-1 DEM) data is used for mapping fault traces and carried out paleoseismic studies to identify paleo-earthquakes. We undertook geomorphological and paleoseismological investigations along the central segment of the KMF zone with the aim of estimating long-term slip rate and recurrence interval of strong earthquakes. Two N-S trenches were excavated across the E-W striking branches of the KMF, named as KMF-1 and KMF-2, revealing that the KMF is dipping towards the north. Detailed studies of the trench walls and optical dating of event horizons have confirmed four earthquakes occurred in the KMF zone between 5600 and 1000 years. The earthquake event I occurred between 5000 and 5500 years; event II occurred between 4000 and 4600 years. The event III occurred between 2000 and 2900 years, and the event IV occurred between 1023 and 1259 AD and 02 BC to 427 AD. Our studies further indicate that the central KMF zone is probably undergoing a quiescent period of ~ 1000 years accumulating the stress in the system to generate a large earthquake. The uplifted and truncated fluvial strath terrace deposits resulting from the Holocene displacements are preserved along the hanging wall block of the KMF. Dividing the elevation of the bedrock strath by their ages yields estimates of the vertical uplift rate of 0.37 to 1.48 mm/year of the hanging wall block of central KMF. With the help of displaced sedimentary units and optical ages, we estimated an average slip rate of 0.28 mm/year and uplift rate of 0.13 mm/year along KMF-1 over an interval of 1800–4000 years. However, the estimated slip rate along KMF-2 is 0.30 mm/year and the observed uplift rate is 0.17 mm/year. The results obtained from the trench investigations along the KMF not only help in understanding the dynamics of KMF but also aid seismic hazard evaluation in the Western Peninsular India.

The 6 November 1774 MI 6 Bolaños Graben Earthquake (Southern Basin and Range Province, West-Central Mexico): Macroseismic Observations and Neotectonic Implications

AbstractThe continental part of west-central Mexico is characterized by the active extensional tectonic regimes of the Trans-Mexican volcanic belt and the adjacent southern Basin and Range Province. The deformation of the latter is distributed over several topographically very pronounced grabens and half-grabens (width 10–20 km, length ≤200 km; throw 1–2 km), including the Aguascalientes, Juchipila, Tlaltenango, and Bolaños grabens. Here, an A.D. 1774–1775 earthquake series in that area is documented based on numerous contemporary sources. The 6 November 1774 mainshock caused moderate-to-severe damage in several communities of the Bolaños graben, including the silver mining town of Bolaños, and moderate damage to communities in the Tlaltenango graben, such as the administrative center of Colotlán. Based on the macroseismic intensity distribution, the epicenter was in the Bolaños graben. The preferred magnitude of the mainshock is ∼6.0±0.5. No major historical earthquake had been reported previously from this region. Existing ground-shaking hazard models may, therefore, give a false sense of security.In the Bolaños graben, motion along the graben-bounding faults and the observed tilting of the graben shoulders has to be mostly younger than the 19.9 Ma age of the youngest basalt of the graben-shoulder stratigraphy. Its correlation across the western master fault indicates a 1300 m throw and a vertical long-term slip rate of 0.07 mm/yr. The observations of alluvial fan deposits juxtaposed against the footwall ignimbrites along the western master fault of the Bolaños graben, the displacement of alluvial fan deposits along secondary faults within the graben, and the existence of hot springs along the western boundary fault all are indicative of active deformation, and so is evidently the A.D. 1774 earthquake.

Hurricane Fault

The Hurricane fault is the big earthquake fault in southwestern Utah. It stretches at least 155 miles (250 km) from south of the Grand Canyon northward to Cedar City and is capable of producing damaging earthquakes of about magnitude 7.0. The Hurricane fault is a “normal” fault, a type of fault that forms during extension of the earth’s crust, where one side of the fault moves down relative to the other side. In this case, the down-dropped side (the hanging wall) is west of the fault; the upthrown side (the footwall) lies to the east. Like most long normal faults, the Hurricane fault is composed of discrete segments that tend to rupture independently (figure 1). The fault lies at or near the base of the Hurricane Cliffs, which form an impressive, little-eroded fault scarp several hundred feet high. Conspicuous, west-tilted, faulted slivers of mostly Triassic and Jurassic red beds are locally exposed at the base of the cliffs, and contrast strongly with gray Permian carbonates exposed in the cliffs themselves. Several Pleistocene basaltic lava flows flowed across and are now offset by the fault zone, dramatically recording long-term slip rates. Should you make the mistake of pronouncing the name “Hurricane” as one would when describing a mighty storm on the East Coast, you should stand to be corrected, for locals pronounce it as “Hurricun” even though pioneers named the town after ferocious winds common to the local area.

Neotectonics and late Holocene paleoseismic evidence in the Plio-Quaternary Daroca Half-graben, Iberian Chain, NE Spain. Implications for fault source characterization

The official seismic hazard models in Spain used in the seismic building codes do not incorporate Quaternary faults, largely due to insufficient data for their proper characterization. There is an obvious need to conduct investigations in most of the recognised Quaternary faults to unambiguously demonstrate their Quaternary tectonic activity and assess their seismogenic potential. This work illustrates the integration of cartographic, tectonic, geomorphological, paleoseismological and geophysical methods for the characterization of the slow-moving extensional Daroca Fault, related to the negative inversion of the Alpine Daroca Thrust, Iberian Chain, NE Spain. Cartographic data indicate that the 27 km long Daroca Fault and the 17 km long Calamocha Fault, separated by a stepover 1.9 km wide, can be considered as segments of the same structure that might rupture jointly and generate Mw7 earthquakes. A long-term slip rate of 0.06–0.02 mm/yr has been estimated for the 27 km long Daroca Fault using an ESR-dated (Electro Spin Resonance) offset pediment. The work discusses why this slip rate is significantly lower than those estimated in nearby normal faults using OSL ages (Optically Stimulated Luminiscence), but comparable with those derived from offset early Pliocene limestones. A trench excavated across the Daroca Fault exposed evidence of the MRE (most recent event) on the fault, with bracketing ages of 2354–1544 cal yr BP (404 BC – 386 AD). This event likely caused the destruction and abandonment of Roman cities in the vicinity of the fault. Several explanations are proposed for the anomalously low vertical displacement of this surface faulting event recorded in the central sector of a 27 km long fault segment: multi-strand rupture, full-segment rupture, partial segment rupture, spillover rupture, and secondary sympathetic rupture.

Dating of active normal fault scarps in the Büyük Menderes Graben (western Anatolia) and its implications for seismic history

Fault scarps, if well-preserved, include precise evidence of past earthquakes. Using cosmogenic 36Cl dating, the timing and slip of paleoearthquakes are recoverable beyond the available earthquake archives. One of the appropriate seismically active regions to apply 36Cl dating is western Anatolia, where its deformation is influenced by an N-S extensional regime, where the horst-graben structures are characterized by normal faults.We have studied well-preserved (meta-) carbonates Kalafat and Yavansu fault scarps in the westernmost part of the Büyük Menderes Graben within western Anatolia. The distribution of cosmogenic 36Cl against height along the fault surfaces indicates that faults experienced minimum three high paleoseismically active phases. The recovered ages of seismic events are ca. 15, 8.4, and 3.6 ka, with vertical components of slip of ca. 0.7, 0.9 and 3.1 m, respectively, for the Kalafat Fault, and ca. 7.9, 3.4, and 2.0 ka with vertical components of slip of ca. 0.6, 3.5, and 2.6 m, respectively, for the Yavansu Fault. The recurrence interval of active periods is generally becoming shortened over time. The ruptures mostly occurred as clustered earthquakes close in time with magnitudes of 6.5–7.1. The vertical slip rates of >0.1, 0.1, and 1.5 mm/yr, and >0.1, 0.8, and 1.9 mm/yr were calculated for the Kalafat and Yavansu faults, respectively. Long-term slip rates were also estimated about 1.0 and 0.6 mm/yr for the Kalafat and Yavansu faults, respectively. Considering the fault lengths, they are capable of producing earthquakes with magnitudes larger than 6.5, and are seismogenic faults.

Holocene seismic activity of the Priene–Sazlı Fault revealed by cosmogenic 36Cl,Western Anatolia, Turkey

Fault scarps in carbonates are structures well suited to 36Cl analysis of paleoearthquakes to reconstruct the seismic history using cosmogenic 36Cl. In this study, we measured cosmogenic 36Cl concentrations in 117 samples along one of the active faults in Western Anatolia, the Priene?Sazli Fault scarp, to reconstruct the age of paleoearthquakes along with their slip amounts, beyond the available historical and instrumental archives. Our results indicate four periods of high seismic activity on the Priene?Sazli Fault since the early Holocene at 8.1 ± 2.0, 6.0 ± 1.5, 3.7 ± 0.9, and 2.2 ± 0.5 ka, with slips of 3.4 ± 0.5, 1.5 ± 0.2, 1.4 ± 0.2, and 1.5 ± 0.2 m, respectively. These ruptures mostly occurred as clusters of earthquakes with magnitudes of up to 6.7?7.0 during the Holocene. Estimated slip rates on the fault are greater than 0.3, 0.7, 0.6, and 1.0 mm/year from the oldest to the youngest modeled earthquakes. In addition, the long-term slip rate is 0.7 mm/year. This means that the Priene?Sazli fault can be considered as a low to moderately seismogenic fault, based upon the recurrence interval.