The Moravosilesian Foreland Basin preserves information of an important interval of the evolution of the eastern European Variscan Orogen. The basin largely was deposited on the Brunovistulian microplate, which underthrusts east-vergent Moldanubian and Moravosilesian units. It hosts an up to 7.5 km thick suite of siliciclastic marine sediments, recording the unroofing of the adjacent Moldanubian zone and the Moravosilesian nappes. Moreover, the basin records polyphase, late-stage Variscan, foreland-affecting deformation occurring between 330 Ma and 310 Ma. Outcrops of the basin can be found in the Drahany upland, southeast of the Czech town of Olomouc and the Nízký-Jeseník mountains, northeast of Olomouc. We conducted zircon U-Pb dating on four detrital samples of a suite of three marine formations in the Drahany upland (Yao et al., 2024). Maximum depositional ages (MDA) of the allochtonous Protivanov (328.7 ± 1.8 Ma), and the parautochthonous Rozstání (326.1 ± 1.0 Ma) and Myslejovice (335.1 ± 2.4 to 329.8 ± 2.4 Ma) formations are coeval to the depositional age of tuff layers within the shallow marine to continental, synorogenic, coal-rich Ostrava formation of the Nízký-Jeseník mountains, which were deposited between 329.2 ± 0.5 Ma and 324.2 ± 0.5 Ma.
This finding challenges the established stratigraphy of the Protivanov, Rozstání and Myslejovice formations, which were previously based on detrital fossiliferous limestone pebbles. The MDAs of all three formations suggest a Serpukhovian rather than Visean depositional age. This has strong implications on the timing of NE-verging basin folding and thrusting. It constraines late-stage Variscan deformation propagation into the foreland to a timespan between <326 Ma (youngest MDA in the Drahany upland) and 303 Ma (opening of the adjacent Boskovice graben (Nehyba et al., 2012)). This timespan postdates time estimates made for compressive tectonics in the region (e.g. Tomek et al., 2019), which proposed the termination of Brunovistulian underthrusting at ~330 Ma.

Nehyba S, Roetzel R and Maštera L 2012 Geologica Carpathica 63 365–82

Tomek F, Vacek F, Žák J, Petronis M S, Verner K and Foucher M S 2019 Tectonophysics 766 379–97

Xiao Y, Rembe J, Čopjaková R, Aitchison J C, Chen Y and Zhou R 2024 Gondwana Research 128 141–60

How to cite: Xiao, Y., Rembe, J., Čopjaková, R., and Zhou, R.: Timing of deformation in the Moravosilesian Foreland Basin – new insights from detrital zircon U-Pb dating, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-18030, https://doi.org/10.5194/egusphere-egu24-18030, 2024.

Granites are generally emplaced several kilometers deep. Therefore, areas where granites younger than ~5 Ma are exposed must have been uplifted and exhumed rapidly. Young granites are distributed along convergent plate boundaries [1]. The Japanese islands, consisting of active island arcs, have some young granites, such as the world’s youngest Kurobegawa granite of ~0.8 Ma [2] in Hida mountain range, central Japan. The Tanigawa-dake area, in the southern end of the Northeast Japan arc, hosts such granites of late Miocene to Pliocene ages ranging from ~6.0–5.5 Ma, ~4.0 Ma to 3.3–3.2 Ma (zircon U-Pb) [3,4]. Previous studies [4] also reported zircon (U-Th)/He dates (ZHe) of 3.3–1.4 Ma and apatite (U-Th-Sm)/He (AHe) dates of 2.8–1.0 Ma for these young granites and the Cretaceous granites. Exhumation rates of 0.3–1.7 mm/yr were estimated by AHe dates and assumption of constant geothermal gradients of 40–60 °C/km [6]. However, the AHe dates might reflect initial cooling phase of the young plutons as well as cooling derived from exhumation, potentially leading to an overestimation of exhumation rates in the Tanigawa-dake area.

This study aims to constrain a more reliable exhumation history. We applied two methods for the youngest pluton (~3.3 Ma): (1) Al-in-Hbl geobarometry [5] to estimate the emplacement depth and (2) 1D numerical simulation of geothermal structure based on heat advection-diffusion-production equation [7] to explore the best cooling/exhumation histories consistent with the reported zircon U-Pb age, ZHe and AHe dates. As a result of Al-in-Hbl geobarometry, solidification pressures of 0.9–2.6 kbar were estimated. Emplacement depths derived from these pressures are 3.4–9.5 km by assuming the granites density of 2.7 g/cm³. Exhumation rates were calculated to be 1.0–2.9 mm/yr for the youngest pluton, assuming an intrusive age of ~3.3 Ma [3]. In the 1D heat advection-diffusion-generation model, the best exhumation rates are ~1.2 mm/yr and the best emplacement depth is ~4.0 km. Comparing with the exhumation rate estimated from the AHe age of ~1.0 Ma [4] in the same pluton (0.8–1.7 mm/yr), the geobarometry method yielded similar or higher exhumation rates (1.0–2.9 mm/yr). Similarly, the modeled rate (1.2 mm/yr) fits with the exhumation rate estimated using AHe age. This indicates that the initial cooling was finished by the time of the AHe date for ~3 Ma pluton, i.e., the previous geothermal structure in this area had relaxed to the current one. Consequently, the exhumation rates calculated from AHe date and current geothermal gradient were consistent with those obtained from the combination of geobarometry, zircon U-Pb, ZHe and AHe datings and numerical thermal modeling.

References [1] Harayama (1992) Geology, 20, 657–660, [2] Ito et al. (2013) Sci. Rep., 3:1306, [3] Minami et al. (2021) EPS., 73:231, [4] Minami et al. (2023) Thermo2023 abstract, p.129, [5] Mutch et al. (2016) Contr. Mineral. and Petrol., 171:85, [6] Tanaka et al. (2010) EPS., 56, 1191–1194, [7] Murray et al. (2018) G-Cubed, 19, 3739–3763.

How to cite: Minami, S., Sueoka, S., Fukuda, S., Malatesta, L. C., Kawakami, T., Higashino, F., Kajita, Y., and Tagami, T.: Separation of exhumation and post-intrusion cooling with thermochronology, Al-in-Hbl geobarometry, and numerical thermal modeling: an example from Central Japan, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-16512, https://doi.org/10.5194/egusphere-egu24-16512, 2024.

Since its onset in the Late Cretaceous, episodic mountain building in the Central Andes has shaped the landscape, climate, and biota of western South America through a series of synchronous regional pulses of intensified deformation and surface uplift acting at the scale of the entire orogen. However, despite this common Late Mesozoic through Cenozoic tectonic history, the ~4000 km long Central Andes exhibit remarkable latitudinal differences in both height and width, pointing to the potential importance of local heterogeneities in controlling the magnitude of topographic growth associated with each of the regional mountain building episodes. A thorough understanding of the driving mechanisms behind these latitudinal differences requires first determining the times, rates, magnitudes and spatiotemporal patterns of crustal thickening and surface uplift along the orogen. While this has been done extensively in recent years for the southern and central portions of the Central Andes, such processes are still insufficiently constrained in its northernmost part.

In this work, we use new and published whole-rock geochemistry data from the Late Cretaceous to Late Miocene arc-related magmatism recorded in northernmost Peru to quantitatively estimate crustal thickening and surface uplift using empirically calibrated “chemical mohometers” based on the ratios of key trace elements. We compare our results with the tectonostratigraphic evolution and tectonic subsidence history of the adjacent foreland and hinterland basins. Finally, we present new apatite U-Th-Sm/He and apatite fission-track thermochronological data from a transect across the northernmost Central Andes. These data, integrated with structural observations and the reconstructed crustal thickening and surface uplift history, unravel the relative contribution of magmatism and shortening to the observed crustal thickening.

How to cite: Marulanda, S., Parra, M., Leon, S., Sobel, E., and Glodny, J.: Quantifying crustal thickening and surface uplift in the northernmost Central Andes, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-991, https://doi.org/10.5194/egusphere-egu24-991, 2024.

The Santa Bárbara System (SBS), located at the Central Andes of northwestern Argentina, is a thick-skinned fold-and-thrust belt (FTB) that represents the outermost portion of the orogenic wedge and the western boundary of the undeformed Chaco-Paraná foreland basin. The present-day structural architecture of the SBS is mainly governed by the reactivation of basement anisotropies and the inversion of Cretaceous normal faults imprinting an overall vergence towards the west. Some of the major faults show evidence of active tectonics in the landscape, which also correlates with instrumental seismicity and destructive earthquakes recorded.

Studies based on seismic interpretation of growth strata in synorogenic deposits have shown that the basement ranges of the southern SBS began to be uplifted during the late Miocene, although the magnitude of exhumation has not yet been quantitatively established. On the other hand, thermochronological analyses of basement samples from the neighboring Eastern Cordillera (EC) have highlighted the relevance of a late Miocene (ca. 10 Ma) exhumation event that propagated the orogenic front into the Mojotoro range, west of the northern SBS.

In this contribution, we present the first (U-Th-Sm)/He cooling ages from Paleozoic rocks of the northern SBS and from the Neoproterozoic basement of the Reyes range, in the EC. The integration of these data with previously published cooling ages allows to conclude that the late Miocene compressional event reached the northern SBS, driving the exhumation of the basement-cored ranges by 7-8 Ma, much earlier than previous estimations. In addition, the Reyes range sample yielded a younger cooling age (ca. 4 Ma) which agrees well with the model of hinterland reactivation of faults due to the recovery of a sub-critical orogenic wedge, as proposed by previous publications.

Based on the available structural reconstructions, an average exhumation rate of ca. 0.7 mm/a can be estimated for the western frontal thrusts of the northern SBS. This value agrees with the late Pleistocene-Holocene rates obtained for neotectonic morphostructures of the Lerma Valley, the easternmost intermontane basin of the EC, suggesting the continuation of a similar deformation pattern throughout the Quaternary for this portion of the Andean back-arc. Additionally, our results shed light on the tectonic evolution style of thick-skinned FTB´s and broken foreland basins.

How to cite: Garcia, V. H., Galetto, A., Sobel, E. R., Payrola, P., Montero, C., Elías, L., Arnous, A., Glodny, J., Hongn, F., and Strecker, M. R.: Onset of compressive exhumation of the northern Santa Bárbara System (NW Argentina). Tectonic implications from low-T thermochronology, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-14954, https://doi.org/10.5194/egusphere-egu24-14954, 2024.

The Coastal Cordillera of Central Chile, recognized as the world's longest coastal mountain range, exhibits notable variations in erosion rates, mean precipitation, vegetation cover, and topography along its expanse. Serving as a natural laboratory, this region facilitates an in-depth exploration of the intricate interplay between tectonics and climate, owing to its distinct climate gradient and unique subduction margin features. Moreover, subduction and migration of the aseismic Juan Fernandez Ridge (JFR) from northern latitudes to its current position (~ 33.5°S) establish distinct subduction erosion conditions in the north and accretion conditions in the south of the ridge. This has implications for the tectonic deformation style of the forearc, potentially influencing the style and timing of uplift.

Across the region, numerous high elevation – low relief surfaces, often surrounded by knickpoints resembling flat mountain tops, offer valuable insights into the temporal aspects of knickpoint formation hence uplift processes, which might reflect the history of the ridge subduction.  Using geomorphometric indices such as steepness, chi, and knickpoint zones along rivers, we conduct a comprehensive analysis of these surfaces. Initial morphological assessments reveal no obvious trend in the distribution of these surfaces along the strike, although their size diminishes from north to south. Additionally, we used in situ cosmogenic ¹⁰Be nuclides to quantify erosion rates at five different flat mountain tops, thereby determining the knickpoint initiation time. Erosion rates are lower above knickpoint than the ones below knickpoints as expected.  Consistently low erosion rates (0.004 mm/yr – 0.07 mm/yr) prevail across the region. Considering the substantial height of these surfaces (approximately 1.5-2 km), the initiation time of the knickpoints might show the history before arrival of the JFR in the south, whereas in the north they might be comparable with the passage of the JFR. However, by incorporating paleoclimate and geodynamic conditions overtime into the landscape evolution model, we anticipate obtaining more precise results for comparison. In conclusion, the Coastal Cordillera of Central Chile undergoes complex interactions among tectonics, seismology, and climate. A nuanced understanding of these processes contributes significantly to broader insights into convergent plate boundaries and the geological evolution of forearcs.

How to cite: Yazici, M., Scherler, D., and Oncken, O.: Unraveling Flat Mountain Tops in the Coastal Cordillera of Central Chile: Based on Erosion Rates, Knickpoints, and Uplift Mechanisms, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-12360, https://doi.org/10.5194/egusphere-egu24-12360, 2024.

Landscape is the integrated product of external forcings (e.g., tectonics and climate) and internal bedrock erodibility. In principle, hard bedrock with low erodibility can steepen rivers in a similar way to tectonic uplift. A key challenge in tectono-geomorphic analysis is thus separating tectonic and lithological effects on landscapes. To address this, we focus on multiple rivers that are transiently incising through contrasting lithologies in the Gulf of Corinth, Greece where tectonic history is broadly well-constrained, and climate is relatively uniform. We first exploit topographic metrics and river long profiles to demonstrate that landscapes are responding to both tectonics and lithology. In particular, the long profiles are divided into knickpoint-bounded segments, and at this scale, channel steepness is shown to be more sensitive to lithology than the entire catchment, possibly due to the relatively uniform uplift rate in the channel segments. We then use segment-scale steepness variations between different lithologies to constrain their relative erodibility (K_lime : K_cong. : K_sand-silt. : K_{p-con sed} = 1 : 2 : 3 : 4), which is further converted into actual lithological erodibility by modelling a well-constrained, ~750ka knickpoint in the Vouraikos. The effectiveness of lithological erodibility is supported by the observation that if lithological erodibility is used to calibrate studied river long profiles in Chi distance, we obtain long profile concavities that fall within the theoretical range. Finally, we use lithology-calibrated metrics to provide new geomorphic constraints on the timing and magnitude of tectonic perturbations. These geomorphic results are interpreted in conjunction with previous studies to shed new light on fault growth and linkage history in the Gulf of Corinth. Our study therefore demonstrates tectonic signals can be isolated from transient and lithologically heterogeneous landscapes by accounting for spatial variability in lithology.

How to cite: Zhou, Z., Whittaker, A., Bell, R., and Hampson, G.: Isolating tectonic signals from transient and lithologically heterogeneous landscapes in the Gulf of Corinth, Greece, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-15558, https://doi.org/10.5194/egusphere-egu24-15558, 2024.

Stream-channel offsets are widely used for identifying strike-slip faults and estimating fault slip rates. Most strike-slip faults have the component of dip-slip motion. Here, we used a landscape evolution model to investigate the role of dip-slip in creating and maintaining stream-channel offsets in the strike-slip environment. Our results show that the length of stream-channel offsets is primarily controlled by the vertical slip rate difference (VSRD) between the above fault part and the below fault part. The average cumulative offsets of the stream channels are positively associated with VSRD and are negatively related to the strike-slip rates. The positive VSRD leads to underestimates of offsets by promoting stream capture while the negative VSRD may lead to overestimates of offsets by creating pre-existing offsets and shutter ridges which inhibits stream capture. Our results call for careful studies of surface processes when using stream-channel offsets to infer fault slip and estimate slip rates.

How to cite: Li, Y., Zhang, H., and Zhao, X.: The role of dip-slip components in creating and maintaining a strike-slip landscape, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-3286, https://doi.org/10.5194/egusphere-egu24-3286, 2024.

Drainage networks are particularly sensitive systems among all the topographic features in terms of their response to perturbations driven by active tectonics. Indeed, fluvial landscapes can record several information about different processes especially in geodynamically active areas, allowing to relate spatial-temporal variation in base-level fall and vertical incision of stream channels with certain morphometric features. This study focuses on the tectonic evolution of the Alessandria Basin, a syn-orogenic tectonic basin located at the junction between the Alps and the Apennines, that experienced progressive subsidence during the overthrusting of the Monferrato Arc (the westernmost outer arc of the Apennine belt) onto the Po Foreland Basin. Different studies carried out in this region have assessed the Neogene tectonic evolution at a regional scale, although Quaternary activity is still poorly understood in terms of both Alps/Apennines uplift and activity of the compressive front of the Monferrato Arc. In this study, we applied river linear inversions to reconstruct the baselevel-fall history of 6 catchments that drain into the Alessandria Basin. We used 9 ¹⁰Be-derived basin-average denudation rates to calculate the erodibility parameter needed for inferring base-level fall rates from previously chi-transformed river profiles. The results describe the last ~ 3 Ma of tectonic activity, highlighting increases in baselevel-fall rate with an initial peak around 3 Ma, and a second around 2 Ma. While the first peak is coeval with the vertical uplift that affected most of the northern-central Apennine, the second one suggests an acceleration in subsidence of the Alessandria Basin concurrently with the uplift of the Monferrato Arc.

How to cite: Buleo Tebar, V., Bonasera, M., Racano, S., and Fubelli, G.: Drainage base-level fall history in North-western Apennines and implications on the Alessandria Basin tectonic activity, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-6673, https://doi.org/10.5194/egusphere-egu24-6673, 2024.

Gilbert-type deltas, built into rift basins, record interactions between fault-driven uplift and subsidence, sediment supply, and drainage network evolution. Typically forming at the junction of progressive fault segments, the syn-rift stratigraphy of uplifted Gilbert deltas offers a preserved record of the dynamic behavior of sedimentary source-to-sink systems through geological time. Of the physical parameters preserved in delta stratigraphy, grain size distributions contain unique information about sedimentary source-to-sink system dynamics over time. Specifically, downstream fining trends in syn-rift deposits reflect interactions between sediment supply to the basin and accommodation space creation driven by active faulting and subsidence. This work aims to understand how grain size distribution can quantify the syn-linkage phase of normal fault segments in the Gulf of Corinth. We examined two Pleistocene geological examples of uplifted Gilbert deltas with distinct tectonic configurations: 1) The Kerinitis Delta, formed by the relatively simple interaction of two same-aged fault segments, the Pirgaki and Mermoussia (P-M) Faults, which experienced a single linkage event; and 2) the more complicated Akrata Delta, formed by multiple linkage events between fault segments of the East Heliki Fault (EHF) and Derveni Fault (DF). We collected gravel grain size distribution data across 62 localities. Additionally, we captured scaled grain-size photographs in inaccessible areas. By tracing stratigraphic units and measuring their thicknesses, we reconstructed hanging-wall subsidence and paleo-fault slip rates. Using a self-similarity-based grain size fining model, we are able to reconstruct sediment supply rates and paleo-catchment erosion rates during the evolution of the fault systems. Further, we reconstructed the catchment averaged erosion rate to be markedly lower than the reconstructed footwall uplift, implying the landscape's transient response to fault growth. Our analysis demonstrates that grain size trends serve as a powerful tool for quantifying the complete growth histories of faults underlying normal fault-driven Gilbert delta systems. We demonstrate the feasibility of converting high-resolution grain size fining patterns preserved in Gilbert delta stratigraphy into reconstructed records of fault slip rates, hanging wall subsidence rates, sediment flux changes, and other key forcing parameters over 10⁵ year timescales. This significantly expands the quantitative toolbox available to translate syn-rift sedimentary architecture into rich chronologies unravelling structural deformation patterns, including fault interactions, segment linkage, and overall progression.

How to cite: Rezwan, N., Whittaker, A. C., Hobley, D., and Zhou, Z.: Quantifying normal fault growth histories from Gilbert Delta stratigraphy using downstream grain size trends: Examples from the Kerinitis and Akrata Delta, Gulf of Corinth. , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-12627, https://doi.org/10.5194/egusphere-egu24-12627, 2024.

The North Tehran Fault (NTF) is the most active tectonic structure crossing the northern fringe of the densely populated megacity of Tehran (Iran). It extends over 68 km and juxtaposes the southern piedmonts of the Central Alborz Mountains (volcanic rocks associated with the Karaj Formation) from the Neogene-Quaternary Tehran Alluvium. The NTF is an oblique-slip fault in which the left-lateral strike-slip faulting accompanies the dominant reverse motion.

The geomorphic features affected by the NTF’s activity appear to be limited and concealed during the past few decades due to the rapid northward expansion of the Tehran metropolitan area. Nevertheless, numerous evident fault outcrops, displaying stratigraphic offsets in various locations along the megacity, are still accessible.

This study selects two fault outcrops inside the city in the western segment of the NTF and a third one in the eastern termination of the NTF close to its junction with the Mosha Fault. These sites were already studied in previous works, however, no reliable geochronological data have been available so far for them. In the first two western sites, the Eocene Karaj Formation rocks were thrust over Quaternary alluvial-colluvial deposits. The subsidiary fault is almost parallel to the main NTF in the second site at Kan, which separates the old alluvial-colluvial deposits in the hanging wall from the younger deposits in the footwall. The third site is located close to the termination of the NTF in the Kond region. Here, remnants of Quaternary fluvial terraces are uplifted by the NTF and form elevated landforms identified in its hanging wall.

To estimate the dip-slip rate for the NTF, we applied luminescence dating to the alluvial-colluvial deposits and fluvial terraces to constrain the deposition time. By incorporating the measured vertical offset for each site, the dip-slip rates of the NTF were established at different locations.

How to cite: Heydari, M., Ghassemi, M. R., Grützner, C., and Preusser, F.: Re-visiting the dip-slip rate of the North Tehran Fault at the northern megacity of Tehran (Iran) using luminescence dating , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-3416, https://doi.org/10.5194/egusphere-egu24-3416, 2024.

Northwestern Dinarides is a region of slow tectonic deformation with rates of 2-4 mm/year. Active deformations are largely accommodated by thrusting and dextral strike-slip faulting. The region exhibits moderate to strong seismicity and swarming events. However, the absence of Quaternary sediments across majority of fault scarps does not allow paleoseismic trenching on active fault segments in order to reconstruct a paleoearthquake record of the area. Even so, Northwestern Dinarides are an analogue for karstic phenomena, such as caves and abundance of speleothem forms in them. Generating the region as an ideal testing ground for speleoseismology. The investigated site of Postojna Cave is a 24 km long cave system, located in SW Slovenia, crosscut by the right-lateral strike slip Dinaric fault system (NW-SE striking). The karstic massif in which the cave evolved is enclosed by two major regional active faults, Idrija, Predjama faults and a smaller, active, Selce fault. Postojna Cave presents a diverse array of speleothem formations, characterized by their various morphologies. Some of these formations exhibit signs of deformation or breakage, with certain instances suggesting possible alteration induced by tectonic and seismic activities.

The investigated speleothems are located in an expansive cave chamber, on a subvertical fault zone with a Dinaric strike. The researched fault had a TM extensometer installed more than 20 years ago, to measure tectonic displacements within the fault. In the years 2009-2010 and in 2014 it exhibited displacements (tectonic transients) coinciding with major regional seismicity. The synchronous displacements and the abundance of deformed speleothems within a singular fault zone is why the location was chosen within the cave for sampling. Speleothems were sampled with a diamond corer in an overall distance of 50 m, along the strike of the fault. Specifically, fractures healed with speleothem in flowstone that is located directly within the fault core zone and on the hanging wall of the fault. Additionally, a few of youngest growth speleothems on fractured columns bridging the hanging wall and the footwall were included.

U-Th geochronology was done on nine sampled deformed speleothems using MC-ICP-MS. The results revealed ages from approximately 55,000 years BP to too recent for analysis (<0.5 ky). Two notable clusters of ages were recognized, 22 and 6.5 ky BP. The majority of the dated speleothems coincide with ages derived from local paleoseismic trenching data, younger than thresholds of 12 ky BP and 8.4 ky BP. Covering the age of youngest deformations on the near Selce fault (12 ky BP) and Predjama fault (8.4 ky BP). The most recent speleothem sample could potential represent deformations attributed to earthquakes that occurred approximately or are younger than 1500 CE. The most plausible interpretation of the dated deformed speleothems suggests that the ages at 22 ky BP and 6.5 ky BP may signify distinct tectonic deformation events, possibly indicative of paleoearthquakes. However, it is important that all speleothems dated as younger than the most recent deformations along the Selce and Predjama faults could potentially represent seismic or aseismic tectonic deformations.

How to cite: Novak, U. and Šebela, S.: A 60.000-year tectonic record: speleoseismology insights from a fault zone, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-6226, https://doi.org/10.5194/egusphere-egu24-6226, 2024.

The Pamir orogen, laying at the northwestern syntaxis of the Indo-Asian collision zone and one of the most tectonically active regions of central Asia, experiences significant extension in its interior. Although internal extension is common in mature orogens, the Pamir is special because (i) its extension is primarily concentrated on the Kongur Extensional System (KES) rather than distributed on multiple normal faults; (ii) the KES is localized at the eastern region of the Pamir rather than centralized, suggesting asymmetric extension; and (iii) extension along the KES decreases southward, instead of decreasing from central portion to its northern and southern ends. Because of these unique characteristics, the causes of internal extension of the Pamir and formation of the KES have inspired numerous investigations, which in turn have led to the proposal of various mechanical models. Defining multi-timescale deformation rates along the KES, especially for late Quaternary and modern slip rate, is prerequisite for better understanding the nature of extension in the Pamir.

In this study, we focus on one of the most debated structure within the Pamir: the nearly NNW-trending Kongur Normal Fault (KNF), the most primary and striking part of the KES. This fault is characterized by dramatically increased topography (elevation up to > 7,500 m) which is expressed as lofty Kongur and Muztaghata massif in its footwall. Thermochronology ages suggest that the initiation, largest magnitude of extension and highest long-term exhumation rates along the KES are in the vicinity of the Kongur massif. Although some studies have focused on determining the tectonic activity of the KES since the late Cenozoic, almost no late Quaternary rates estimate yet exists on active fault (KNF) bounding the Kongur massif. Moreover, Glaciers have oscillated considerably throughout the Quaternary at Kongur and Muztaghata massif, offering a unique opportunity to expand our understanding of the role of glaciers in shaping the topography.

At Bulunkou, the KNF is branched into two segment. The surface trace of the both segments of KNF is clearly visible as a straight line feature, and characterized by offsets of different geomorphic surfaces. We determined the Holocene slip rates of both segment of KNF through geomorphic mapping on high-resolution DEMs and cosmogenic ¹⁰Be exposure dating of boulders on displaced geomorphic surfaces. Finally, we observed a very high Holocene slip rates (even probably can reach to 10-13 mm/a) of KNF at Bulunkou. Correlating our new observations of KNF with kinematics and slip rates along the whole KES, we clarify the role of the KES in accommodating internal extension of the Pamir.

How to cite: Liu, Q., Chen, J., Li, T., Xu, J., Di, N., and Luo, M.: Mechanical Models for East-West Extension within the Pamir Orogen: Insights from of the Holocene slip rate of the Kongur Normal Fault, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-7399, https://doi.org/10.5194/egusphere-egu24-7399, 2024.

Vertical–axis rotations recorded by paleomagnetic results from the northeastern Tibetan Plateau afford new insights into the tectonic processes related to the growth of the Tibetan Plateau. The Qinling Mountain is a special orogenic belt that bridges the crustal shortening of the northeastern margin of the Tibetan Plateau in the west with the extensional North China block in the east. In this study, we focus on the intermountain basins across the West Qinling Mountain. We present geochronological and paleomagnetic results from the basalt and redbed sequences from the Cretaceous–Cenozoic basins within the West Qinling Mountain. Constrained by precise ages, our paleomagnetic results reveal that approximately 10–20◦ clockwise vertical–axis rotation occurred across the West Qinling Mountain during the middle to late Miocene, indicating a significant period of outward growth of the Tibetan Plateau.

How to cite: Huang, R. and Wang, W.: Cenozoic clockwise rotation of the northeastern Tibetan Plateau, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-15504, https://doi.org/10.5194/egusphere-egu24-15504, 2024.

A comprehensive, interdisciplinary study was carried out to investigate the characteristics of the 1967 magnitude 7.1 earthquake along the right-lateral strike fault in Mogod, Mongolia. This fault consists of three segments—two strike faults and a reverse fault spanning from north to south. Recent research revealed a 25 ka cycle in the movement of the reverse fault segment located in the south (Bollinger et al., 2021).

To understand two remaining faults, four excavation surveys (T1, T2, T3, T4) were conducted along the two northern segments. Optically Stimulated luminescence (OSL) was used to track the deposition period in unconsolidated sedimentary layers where surface ruptures occurred, aiding in estimating the recent earthquake of the fault. An additional excavation survey was conducted near the river crossing the fault (at location T4) to determine the thalweg for evaluating geological displacement over the geological timescale.

The excavation results revealed Quaternary surface ruptures in three trenches with OSL sampling. A total of 51 samples were respectively collected from Trench T2 (24 samples), T3 (18 samples), and T4 (9 samples). The Quaternary sediment layers have been deposited since the Last Glacial Maximum (LGM), around ~20 ka. Excavation sites (3 upstream and 4 downstream) intersecting the fault line (T4) aimed to assess displacement caused by seismic activity.

In summary, seismic movements resulting in surface ruptures were detected in the northern two segments around the 20 ka. Further analysis would provide a more precise earthquake recurrence cycle, potentially revealing the timing of subsequent seismic events. Furthermore, completion of the identifying the thalweg, it is expected to reveal the slip rate over geological time scales.

How to cite: Kim, D.-E., Choi, J.-H., Klinger, Y., Lee, T.-H., Lee, H., Cheon, Y., and Choi, Y.: Preliminary study on the characteristics and slip rate of the Quaternary fault in Mogod, Mongolia, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-14293, https://doi.org/10.5194/egusphere-egu24-14293, 2024.

The Makran Subduction Zone (MSZ) of Iran and Pakistan, where the oceanic Arabian plate is sinking beneath the overriding continental Eurasian plate, is among the least explored subduction zones. Limited geodetic measurements, especially in the Western MSZ (WMSZ) with lower seismicity, have posed challenges in assessing the potential for future seismic events. The extensive spatial coverage offered by the Interferometric Wide-Swath (IW) mode of Sentinel-1 Interferometric Synthetic Aperture Radar (InSAR) allows for measuring tectonic deformation at a scale of millimeters per year across distances spanning hundreds of kilometers. Nevertheless, the presence of other signals and errors­­­­­—with similar spatio-temporal patterns to the signal of interest—poses challenges to accurately estimating the low-amplitude, large-scale subduction-induced deformation from InSAR observations.

In this contribution, we analyze more than eight years of continuous Sentinel-1 InSAR data from both ascending and descending orbits in the WMSZ area of Iran, to capture the Line-Of-Sight (LOS) interseismic crustal deformation rate. Our approach integrates a comprehensive and novel atmospheric mitigation strategy, accompanied by corrections for non-tectonic processes and rigid plate motion, aiming to isolate the tectonic-related signal from other non-tectonic signals and errors. In the following step, we investigate three trench-perpendicular profiles to infer the spatial and along-dip distribution of plate coupling from the Line-Of-Sight (LOS) deformation rates obtained through InSAR.

Due to the limited InSAR coverage near the trench (as located beneath the sea), it is not possible to constraint coupling in that area that extends 150 km far from the trench and reaches a depth of 10 km. Our findings reveal significant variations in interseismic coupling from west to east. We observe regions of weak and strong coupling, located near Jask (the westernmost part of the WMSZ) and Chabahar (the easternmost part of the WMSZ), respectively. The middle profile, located near the epicenter of a 5.9 magnitude earthquake that occurred in 1989 (Mw 5.9), exhibits a moderate coupling of 65 percent. Additionally, the coupling is notably high at depths between 10 and 20 km, gradually decreasing to zero at depths between 30 and 40 km.

In summary, the enhanced spatial resolution of InSAR, along with the high precision of deformation rates provided by the advanced error mitigation on the long time series of Sentinel-1 significantly improves our ability to characterize the locking depth at which the boundaries between two plates are accumulating stress in WMSZ.

How to cite: Sobouti, A., Samiei Esfahany, S., Sharifi, M. A., Abolghasem, A. M., Bahroudi, A., and Friedrich, A. M.: Sentinel-1 Insights into interseismic coupling along the plate boundary of the Western Makran Subduction Zone, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-15246, https://doi.org/10.5194/egusphere-egu24-15246, 2024.

In the frame of FURTHER project, “The role of FlUids in the pReparaTory pHase of EaRthquakes in Southern Apennines”, (https://progetti.ingv.it/en/further), consisting in a multidisciplinary study based on seismological, geodetic, and geochemical observations to understand the role of fluids in the seismogenic processes in the Southern Apennines, we focus on the geodetic monitoring at Mefite d’Ansanto (AV) deep CO2 degassing area located at the northern tip of the Mw6.9, 1980 Irpinia fault. Mefite d’Ansanto represents the largest low-temperature non-volcanic CO2 emission of the Earth (Chiodini et al. 2010).

To provide an improved picture of the regional crustal deformation and investigate the relationship among deformation, crustal fluids, and physical-hydraulic properties pattern, we installed a new GNSS network and realized a detailed Digital Elevation Model (DEM).

The new local GNSS network, MefiteNet, consists of four stations (one permanent and three survey-style stations) that monitor the degassing area of approximately 1 km² by April 2022.

Two aerial photogrammetric surveys were performed over Mefite area with a quadcopter drone to obtain a high-resolution Digital Elevation Model (DEM) to estimate the amount and the morphological variations of the Mefite lake level in space and time. The flight technique, that takes into account the topography, was chosen to ensure a constant pixel size on the ground and avoid lack of aerial coverage.

We show the first results of the GNSS data analysis recorded by the MefiteNet and the preliminary results regarding morphological analysis.

How to cite: Esposito, A., Doumaz, F., Galvani, A., Iannarelli, M., Palano, M., Pietrantonio, G., Riguzzi, F., Sepe, V., Sparacino, F., and Trippanera, D.: Deformation at Mefite d’Ansanto area (Italy) through an interdisciplinary approach: GNSS Network and Digital Elevation Model, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-17056, https://doi.org/10.5194/egusphere-egu24-17056, 2024.

Recent studies on natural and experimental seismic faults have revealed that frictional heating plays an important role in earthquake dynamics. We report IRSL and IRPL signals changes in the granite rock after frictional experiments. Our results indicate that high-rate (2.0 m/s) frictional heating during seismic events can reset the 'geologic clocks' of fault rocks. Thus, the IRSL and IRPL signal in granite from natural fault zones has the potential to directly constrain the age of seismic events. Whereas low-rate (2.0 mm/s) frictional slip, even over long times (1000 s), does not reset the IRSL and IRPL signals in granite. The result is similar to the quartz gouge（Hui Li Yang., et al., 2019）.

How to cite: Yang, H., Chen, J., Cui, F., and Kook, M.: Resetting of IRSL and IRPL signals by frictional heating in experimentally sheared Granite rock at seismic slip rates, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-14396, https://doi.org/10.5194/egusphere-egu24-14396, 2024.

Hualien City in Taiwan is situated in the northernmost segment of the Longitudinal Valley, transitioning from the subduction of the Philippine Sea Plate to a collision environment. It is one of the most seismically active regions in Taiwan. The Milun Fault, a significant active fault, traverses through the urban area of Hualien, causing an uplift of the Milun Terrace and deformation and fracture of Milun gravel rocks in the hanging wall. The Milun Fault was the seismogenic fault for the 1951 Hualien earthquake (ML 7.3) and experienced approximately 70 cm of horizontal displacement triggered by the 2018 earthquake. The proximity of the Milun Fault to several secondary fault systems indicates complex structural activity.

This study focuses on observing the gravel rock layers beneath the Milun Tableland along the northern coast, utilizing a well-cemented beachrock layer as a key bed to assess variations in uplift across different areas.  Based on the investigations, the gravel rock layers beneath the Milun Tableland can be broadly divided into three zones:(a) Southeast Stable Zone: Characterized by a low beachrock layer height of approximately 3 meters. Minimal evidence of fault activity is observed in this area. (b) Damaged Zone (Middle): Marked by a beachrock height reaching up to 4.5 meters. Multiple fault systems are developed within the gravel rock layers, leading to fragmentation and damage. (c) Northwest Stable Zone: With a beachrock height of less than 1 meter, this area shows observable fractures in the underlying gravel rock but lacks clear structural activity. Measurements of slickenside and identification of fracture axes in the gravel rocks provide the maximum stress direction for each zone, indicating stress orientations ranging approximately between 160-170. The inferred trend of the Principal Displacement Zone (PDZ) aligns with a strike of 010, consistent with the surface rupture observed during the 2018 Hualien earthquake.

The field data from this study can offer additional information about the Milun Fault system. By incorporating the analysis results of surface rupture caused by the earthquake in 2018, it can further confirm the flower structural characteristics of the Milun Fault system. Additionally, it allows for observing other motion features associated with lateral fault movements.

How to cite: Hsu, Y.-C., Chang, C.-P., Huang, S.-Y., Wang, C.-C., and Yen, J.-Y.: Exploring Structural Activity Through Gravel Rock Fracture Characteristics: A Case Study of the Milun Fault in Hualien, Taiwan, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-6996, https://doi.org/10.5194/egusphere-egu24-6996, 2024.

Faulting and folding of basement rocks together accommodate convergence within continental orogens. Here we use the river terraces sequences along the Dongda river as the geomorphic tracer to examine deformation patterns at the northeastern Qilian Shan. Five river terraces, T1 (youngest), T2, T3, T4a and T4b (oldest), were identified and dated as 4.2 ± 0.3 ka, 6.1 ± 0.5 ka, 12.4 ± 2.5 ka, 16.4 ± 0.2 ka and 27.4 ± 2.5 ka, respectively. Three major reverse faults, Minle-Damaying fault, Huangcheng-Ta’erzhuang fault, and Fengle fault, contribute to deformation of the region. Based on displaced terrace treads, we estimated the vertical slip rate along the Minle-Damaying fault as 0.7–1.2 mm/a, along Fengle fault as 0.5–0.7 mm/a. Apart from surface displacement across faults, folding of the Dahuang Shan anticline at the hangingwall of Fengle fault adds to an additional uplift rate of ~ 0.2 mm/a at its crest. Inhomogeneous uplift of the intermontane basins between Minle-Damaying fault and the Dahuang Shan anticline indicates a 0.9 ± 0.2 mm/a uplift rate along the Huangcheng-Ta’erzhuang fault. Kinematic modeling shows that the deformation propagated from North Qilian to the foreland along a south-dipping 10° décollement which rooted Haiyuan fault at the depth of 20–25 km, accommodating 2.7–3.8 mm/a total crustal shortening rate. We suggest that the thrusts formed and high strain rate at eastern Qilian as a results of strain partitioning within the Haiyuan-Qilian systems, might coincided with the restraining bend of Haiyuan fault system, and strain rate within this complex structure may bear high regional seismic hazard.

How to cite: Hu, X. and Wang, Y.: The thrust structure and slip partitioning of Haiyuan-Qilian systems at NE margin of Tibetan plateau, constrained from geomorphic evidence , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-9405, https://doi.org/10.5194/egusphere-egu24-9405, 2024.

Repeated reoccurrence of the low to moderate intensity earthquakes in the Central India region for a long period scruples its acceptability as a stable continental region. In last five years, the National Centre for Seismology INDIA has reported a 27 number of earthquakes of low to moderate intensity around the Tan Shear Zone (TSZ) and Balrampur Fault geofracture in the eastern part of the Central India Tectonic Zone. Moreover, the presence of steep geothermal gradient recorded in the area, only along the aforementioned lineaments, maybe considered as an indirect evidence of frictional heat generation due to seismic/aseismic creep related to tectonic rejuvenation. The kinematics of this reactivation of preexisting structural heterogeneity under the present tectonic configuration is not well understood in this area. The present study has been conducted to address this issue of tectonic reactivation in the area specifically confined between Tan Shear Zone in the north and Balrampur Fault in the south. The Differential Interferometric Synthetic Aperture Radar (DInSAR) technique has been adopted to understand the kinematic of ground movement due to a very recent earthquake event (dated 24 March 2023 with intensity of 3.9) in this zone of interest.   Furthermore, a few numerical experiments have been carried out using finite element method (FEM)  to model the possible influence of preexisting heterogeneity on strain localization in response to current tectonic setup around the study area. In numerical model, we have assumed a hypothetical graben, formed by gravity sag in granitic rheology, filled with layer of sedimentary rheology, equivalent to Gondwana rocks.

Through the DInSAR analysis of SLC image pairs, it has been revealed that the central part spanning ~25 Km length exhibits nearly uniform rate of upliftment due to the earthquake event. The axis of uplift flanked by an undisturbed zone Toward TSZ in the south and the Balrampur Fault in the north, shows a trend parallel to the boundary of Son-Mahanadi graben. For a plausible explanation of the uplift paralleling the preexisting steep graben boundary several hypothetical set-ups were tried with FEM as explained above. Thereby, it has been enumerated that even though the geometric reactivation of the steep graben boundary fault in the reverse-slip mode was not possible, due to stress-buttressing with the preexisting mechanical heterogeneity a hanging wall-cut reverse fault nucleated from the graben collar. Uplift due to this reverse fault resemblance the axial uplift in the study area by its position and orientation with respect to the preexisting structural heterogeneity. This study with multidisciplinary approaches can be considered as a classic example of shallow brittle failure causing seismicity in any Stable Continental Region.

How to cite: Ali, M., Behera, A., and Bhattacharjee, D.: Influence of pre-existing structural weakness on active tectonics in the eastern part of cratonised Peninsular India: An integrated approach of DInSAR and Numerical Modelling., EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-14384, https://doi.org/10.5194/egusphere-egu24-14384, 2024.