Tectonophysics最新文献

{"title":"Morphostructural evidence of crustal-scale, active along-strike segmentation of the Umbria-Marche Apennines, Italy","authors":"","doi":"10.1016/j.tecto.2024.230527","DOIUrl":"10.1016/j.tecto.2024.230527","url":null,"abstract":"<div><div>This paper discusses the response of topography and river networks to non-uniform lithology and tectonic forcing in the Umbria-Marche sector of the Apennines fold and thrust belt. We ruled out the role of variable erosion of rock types and interpret channel steepness data in terms of rock uplift, discovering a southward increase in the total amount of uplift. Such a trend appears as the large-scale response to uneven vertical motions of different sectors of the mountain ridge and foothills. The general coincidence between sector boundaries and transversal, NE-SW striking faults mapped by seismic interpretation in the outer zone of the fold and thrust belt, suggests that such faults extend to the SW, beneath the allochthonous thrust sheets of the mountainous area. Therefore, it may be inferred that such transversal faults represent long-lived, deeply rooted basement structures compartmentalizing both the axial and the outer zones of the fold and thrust belt. We suggest that differential uplift was essentially controlled by variable amounts of basement thrust displacement characterizing the compartmentalized belt. This interpretation deviates from a more conventional view that uplift of the central Apennines, particularly prominent in the south, is dynamically supported. Our results, besides shedding new light into the active tectonic behavior of a large portion of the Italian peninsula, also provide general insights into the surface response to the differential behavior of crustal blocks produced by along-strike segmentation of active mountain belts.</div></div>","PeriodicalId":22257,"journal":{"name":"Tectonophysics","volume":null,"pages":null},"PeriodicalIF":2.7,"publicationDate":"2024-10-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142418536","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Crustal and uppermost mantle S-velocity structure of the Seoul metropolitan area on the Korean Peninsula from Helmholtz tomography","authors":"","doi":"10.1016/j.tecto.2024.230518","DOIUrl":"10.1016/j.tecto.2024.230518","url":null,"abstract":"<div><div>The Seoul metropolitan area, the most densely populated part of the Korean Peninsula, features complex subsurface structures and seismogenic faults, though their characteristics remain ambiguous due to low seismicity and limitations in fault investigation. High-resolution velocity models can provide constraints for identifying subsurface faults by detecting elongated low-velocity anomalies along fault zones. Recently, a dense seismic network was deployed in this area, facilitating the use of Helmholtz tomography, an array-based method that accounts for finite-frequency effects. Utilizing Helmholtz tomography, we obtained a high-resolution S-wave velocity model down to a depth of 50 km with waveform data recorded at 74 broadband seismic stations. We found that a linear low-velocity anomaly along the Pocheon fault extends to the uppermost mantle, with an increasing width with depth. In contrast, the Dongducheon fault, which traverses Seoul from north to south, is not well imaged, indicating its current weak activity. Another linear low-velocity anomaly extends southwest through Seoul from northern Seoul, potentially representing the extension of the Pocheon fault based on similar strike and dip directions. Additionally, a large lateral low-velocity anomaly is identified in the lower crust beneath the northern part of the Seoul metropolitan area, interpreted as a ductile décollement, connected with the Pocheon, Wangsukcheon, and possibly Gyeonggang faults. This study successfully identified the extensions and orientations of subsurface faults beneath the Seoul metropolitan area down to the uppermost mantle, which is critical for seismic hazard predictions and earthquake simulations in this highly populated area.</div></div>","PeriodicalId":22257,"journal":{"name":"Tectonophysics","volume":null,"pages":null},"PeriodicalIF":2.7,"publicationDate":"2024-10-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142418528","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Variscan basement tectonics and Alpine shear zones in the external Balkanides: Structural data from the Vezhen Massif, Central Stara Planina Mts., Bulgaria","authors":"","doi":"10.1016/j.tecto.2024.230515","DOIUrl":"10.1016/j.tecto.2024.230515","url":null,"abstract":"<div><div>The Alpine Balkanides in Bulgaria are developed over Variscan orogenic fragments, which are variously affected by late-stage thick-skinned thrust tectonics. Often, these fragments hold both Variscan and Alpine structural records. А key area to shed light on important aspects of the tectonic evolution of the external parts of the Alpine Balkanide orogen is the Vezhen Massif in the Central Stara Planina Mountains. Although it is built exclusively of Paleozoic crystalline rocks, its structure was long considered as an example of intense mid Eocene to early Oligocene (Late Alpine) shortening. Detailed fieldwork in the area shows a more complicated tectonic framework and provides evidence of a polyphase structural evolution, involving an important stage of Variscan metamorphism and deformation and two stages of north-vergent Alpine shortening. The Stargel-Boluvanya Tectonic Zone that affects the western Vezhen Massif is one of the most important Variscan structures in the Balkan fold-and-thrust belt. Structural data indicate that the metamorphic basement records initial top-to-north thrusting, followed by further shortening, which led to folding and localized strike-slip deformation. The Variscan <em>syn</em>-metamorphic fabric is cross-cut by several post-kinematic igneous bodies of late Carboniferous to Permian ages. The tectonic history continues with a development of a network of greenschist facies north-vergent mylonitic zones for which an Early Alpine (post-late Permian but pre-Late Cretaceous) age is assumed. Late Alpine north-vergent thrusting is evident only on the eastern and northern flanks of the Vezhen Massif. In a broad structural context, the documented record in the basement rocks of the Vezhen Massif is comparable with those of the external massifs of the Alps and Iberia.</div></div>","PeriodicalId":22257,"journal":{"name":"Tectonophysics","volume":null,"pages":null},"PeriodicalIF":2.7,"publicationDate":"2024-10-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142433754","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Constraining the slip history of the Katschberg normal fault (Eastern Tauern Window) by thermo-kinematic modeling: Implications for the tectonic evolution of the Eastern European Alps in the late Cenozoic","authors":"","doi":"10.1016/j.tecto.2024.230514","DOIUrl":"10.1016/j.tecto.2024.230514","url":null,"abstract":"<div><div>The Katschberg normal fault borders the Tauern Window to the east and played a crucial role during Miocene lateral tectonic extrusion in the Eastern European Alps. In this study, we present new cooling ages from low-temperature thermochronology as well as thermo-kinematic models, which constrain the exhumation history of the Penninic units in the footwall of the Katschberg normal fault and its slip history. Zircon and apatite fission track and apatite (U–Th)/He ages from footwall units range from 16.0 ± 1.9 Ma to 12.8 ± 1.4 Ma, 10.4 ± 1.8 Ma to 7.9 ± 1.3 Ma and 8.2 ± 0.8 Ma to 3.9 ± 0.4 Ma, respectively. Thermo-kinematic modeling indicates that the Katschberg normal fault was active between 21.1 ± 1.8 Ma and 12.2 ± 1.3 Ma and accommodated 27 ± 6 km of crustal extension at a total rate of 3.5 ± 0.3 km/Myr. After the end of normal faulting, exhumation continued with a rate of 0.21 ± 0.06 km/Myr until 2.0 ± 0.5 Ma and with a rate of 0.84 ± 0.08 km/Myr until present. A comparison with another Miocene low-angle normal fault in the Eastern Alps – the Brenner fault – reveals that the amount of extension accommodated by these faults decreases from west to east, which is consistent with an eastward decrease in N-S shortening. Therefore, Miocene deformation is greatest in the western Tauern Window near the Brenner normal fault where shortening in front of the Adriatic Indenter is at its maximum.</div></div>","PeriodicalId":22257,"journal":{"name":"Tectonophysics","volume":null,"pages":null},"PeriodicalIF":2.7,"publicationDate":"2024-09-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142326466","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Stress heterogeneity in the eastern Tibetan Plateau and implications for the present-day plateau expansion","authors":"","doi":"10.1016/j.tecto.2024.230513","DOIUrl":"10.1016/j.tecto.2024.230513","url":null,"abstract":"<div><div>The eastward expansion of the Tibetan Plateau has resulted in different earthquake types in the eastern Tibetan Plateau, but the mechanism remains unclear. Here, we construct a three-dimensional visco-elastoplastic finite element model considering the topography to investigate the influence of fault geometry and rheological heterogeneity on stress fields. In our best-fitting model, the minimum principal stress is nearly vertical around the southern Huya fault zone, which is adjacent to the Longmen Shan fault zone, due to the significant mid-lowerWE crust lateral rheological heterogeneity, and the thrust stress regime accounts for the reverse fault and thrust-dominated earthquakes. In this scenario, the eastward horizontal motion of the mid-lower crust is obstructed and facilitates thrust faulting, suggesting the limited eastward expansion of the Tibetan Plateau. In contrast, the northern Huya fault zone, one of the terminal branches of the East Kunlun fault, accommodates the continuous eastward extrusion of the East Kunlun fault, where the stress regime under a more homogenized crust favors the strike-slip faulting process, along with the dominant strike-slip earthquakes. Moreover, the best-fitting of stress regime explains the thrust-dominated 2008 Ms. 8.0 Wenchuan and 2013 Ms. 7.0 Lushan earthquakes on the Longmen Shan fault zone. Combining geophysical and geodetic observations and model analyses, we propose that the hybrid deformation mode in the eastern Tibetan Plateau is accommodated by upper crustal shear and thrusting deformation and mid-lower crustal thickening driven by the gravitational potential energy gradient. Our results elucidate the mechanism for differences in strong historical earthquakes and, more importantly, isolate the effect of fault geometry from those of heterogeneous viscosity on crustal deformation and stress heterogeneity in the eastern Tibetan Plateau.</div></div>","PeriodicalId":22257,"journal":{"name":"Tectonophysics","volume":null,"pages":null},"PeriodicalIF":2.7,"publicationDate":"2024-09-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142329780","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Using contrasts in horizontal P-wave reflectivity to map the base of the continental lithosphere: Results for the central and eastern U.S.","authors":"","doi":"10.1016/j.tecto.2024.230512","DOIUrl":"10.1016/j.tecto.2024.230512","url":null,"abstract":"<div><div>Vertical-incidence seismic reflection profiles generated from global phases for 16 earthquakes recorded by stations of the Transportable Array (TA) show distinctive patterns of P-wave reflectivity in the uppermost mantle beneath the central and eastern United States. The overall distribution of reflections identified objectively using the sign test statistic applied to bootstrapped stacks is consistent with a westward increase in depth of the lithosphere-asthenosphere boundary (LAB) from roughly 110 to 250 km that is marked within the lower lithosphere by piecewise continuous segments of elevated horizontal P-wave reflectivity. For some profiles, the onsets of zones of increased reflectivity closely match depths corresponding to the maximum negative S-wave velocity gradients found by surface-wave tomography, suggesting that P-wave reflectivity can be used to help characterize properties of the lower lithosphere. We suggest that the vertical change in horizontal reflectivity straddles the lithosphere-asthenosphere transition, encompassing a broad zone of layering caused by increased strain in the lower lithosphere as well as drag-induced flow in the asthenosphere. Some of the lines also show waveforms that fall within the depth range of arrivals identified as midlithospheric discontinuities (MLDs) in overlapping Sp receiver-function profiles. The reflection waveforms observed in the TA lines are mostly multicyclic with a mix of polarities indicating a layered transition, consistent with previous observations and model studies that show the breakup of single Sp waveforms into a series of less prominent, shorter-period P-wave reflections as the dominant frequency of incident energy is increased.</div></div>","PeriodicalId":22257,"journal":{"name":"Tectonophysics","volume":null,"pages":null},"PeriodicalIF":2.7,"publicationDate":"2024-09-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142528999","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Seismic structure of Iceland revealed by ambient noise Rayleigh wave tomography","authors":"","doi":"10.1016/j.tecto.2024.230511","DOIUrl":"10.1016/j.tecto.2024.230511","url":null,"abstract":"<div><div>As it is an ideal location for studying plume–ridge interactions, a clear image of the Icelandic upper mantle structure is necessary. We collect continuous seismic records from 164 stations and extract Rayleigh wave dispersion curves via the frequency-Bessel (F-J) transform method. Based on ambient noise tomography, we provide a new shear-wave velocity model of the Icelandic crust and uppermost mantle, extending to a depth of 120 km. The model is validated by the waveform simulation method and reveals extensive crustal low-velocity zones (LVZs) across both the neovolcanic and nonvolcanic zones of Iceland. These crustal LVZs may be attributed to elevated temperatures, partial melting, and lithological variations. A distinct LVZ beneath a depth of 60 km, mainly on the North American Plate, may correspond to Icelandic plume material. Additionally, hot plume material may be delivered to the crust through low-velocity conduits beneath the spreading mid-ocean ridge. There is a clear contrast between the uppermost mantle low-velocity zones (UMLVZs) in the western region and the uppermost mantle high-velocity zones in the eastern region, which may indicate asymmetric tectonic plates on both sides of the mid-ocean ridge. This asymmetry may be attributed to the multiple eastward jumps of the ridge systems. The eastern high-velocity body, meaning a cooler uppermost mantle than that of the western region, may act as a barrier to obstruct the eastward plume flow. Under plume–ridge interactions, plume material can affect crustal accretion and feed volcanic activity on the surface along the spreading Mid-Atlantic Ridge.</div></div>","PeriodicalId":22257,"journal":{"name":"Tectonophysics","volume":null,"pages":null},"PeriodicalIF":2.7,"publicationDate":"2024-09-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142418588","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"The Crust-Mantle Interaction of the Qiangtang Terrane: New evidence from the Effective Elastic Thickness of the Lithosphere","authors":"","doi":"10.1016/j.tecto.2024.230510","DOIUrl":"10.1016/j.tecto.2024.230510","url":null,"abstract":"<div><div>The crust-mantle interaction in the Qiangtang terrane is significant to study continental rheology and evolution. Its mechanism remains a subject of considerable debate for the reason of lack of sufficient geophysical evidence. The effective elastic thickness (<em>T_e</em>) of the lithosphere can provide important constraints on this issue because it is sensitive to the state of mechanical coupling between the crust and the lithospheric mantle. We present new high-resolution <em>T_e</em> of the Qiangtang terrane by using the multitaper admittance method with fusion of different window, based on satellite gravity and topographical data. Thus, a detailed study of the lithosphere is conducted, for the first time to utilize the spatial variations of <em>T_e</em> and associated parameters, including thermal structures of the lithosphere, uppermost mantle seismic Pn-velocity, and crustal deformation. The results indicate that crust-mantle interaction in the Qiangtang terrane primarily occurs in the middle Qiangtang terrane (87°E ∼ 95°E, 32°N ∼ 34°N), where Te values are lower. In the eastern and western Qiangtang terrane, <em>T_e</em> values are higher, implying weaker late-stage modification. Due to Rayleigh-Taylor instability, lithospheric delamination occurred beneath the south Qiangtang terrane. Based on the extent of these low <em>T_e</em> values (<em>T_e</em> &lt; 50 km), we conclude that the delaminated lithospheric slab sinking into the mantle is ∼400 km in length and elongated in shape. The delamination induces the upwelling of mantle material, upward stress, volcanic activity, extensional faults, and hot springs in the Qiangtang terrane.</div></div>","PeriodicalId":22257,"journal":{"name":"Tectonophysics","volume":null,"pages":null},"PeriodicalIF":2.7,"publicationDate":"2024-09-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142316197","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Spatially-varied crustal deformation indicating seismicity at faults intersection in the SE margin of the Tibetan Plateau: Evidence of S-wave splitting from microseismic identification","authors":"","doi":"10.1016/j.tecto.2024.230509","DOIUrl":"10.1016/j.tecto.2024.230509","url":null,"abstract":"<div><div>The Sanjiang Lateral Collision Zone (SLCZ) in the SE margin of the Tibetan Plateau is a special area where several strike-slip faults intersect, resulting in strong deformation and frequent earthquakes. We employ seismic waveforms recorded by a dense temporary broadband array (SJ array) and regional permanent stations to construct more complete microseismic catalogs by the microseismic identification in the SLCZ. New microseismic catalogs effectively increase the number of small earthquakes, revealing the details of the fault structures and providing many more records for S-wave splitting (SWS) analysis. It provides with an uncommon opportunity to detect the detailed upper crustal anisotropy in the fault intersection zone of SLCZ and to dissect the influence of faults, such as the Lijiang-Xiaojinhe fault and Red river fault, on crustal deformation. The spatial distribution of SWS parameters suggests multiple disturbance mechanisms to the upper crustal anisotropy in the study zone. Spatial distribution of <em>dual</em> dominant polarization directions of fast S waves near the block boundary faults uncovers the stress-focus range. Strong deformation from SWS data indicates frequent local seismicity. It reveals the spatial upper crustal deformation indicated by SWS parameters is closely related to not only stress, fault and local structure, but also local seismicity.</div></div>","PeriodicalId":22257,"journal":{"name":"Tectonophysics","volume":null,"pages":null},"PeriodicalIF":2.7,"publicationDate":"2024-09-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142320135","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Deformation and melt–rock interaction in the upper mantle: Insights from the layered structure of the Horoman peridotite, Japan","authors":"","doi":"10.1016/j.tecto.2024.230508","DOIUrl":"10.1016/j.tecto.2024.230508","url":null,"abstract":"<div><p>To obtain a better understanding of melt–rock interactions in the upper mantle, microstructural and petrological analyses were conducted on deformed mantle peridotites from the Horoman peridotite complex, Hokkaido, Japan. The Horoman peridotite complex is lithologically heterogeneous and contains various kinds of ultramafic and mafic rocks. We studied an outcrop of 3 × 70 m in size that contains layered spinel harzburgite, plagioclase lherzolite, and mafic rocks. The results indicate that reactive melts migrated preferentially along the foliation in the already deformed peridotite, and that these melt-rich zones became especially prone to further deformation. This inference is supported by (1) the parallelism of the boundaries of rock layers and foliation in the deformed peridotite, and the shape and crystallographic preferred orientations (SPOs and CPOs) of olivine in the peridotites; (2) the diffusive trends of magnesium and modal compositions of pargasite grains near the boundaries between peridotite and mafic layers; (3) variations in the NiO content of olivine crystals; (4) variations in olivine CPOs with orthorhombic (010)[100] slip system patterns and weak fiber-[010] patterns; and (5) the strong pargasite SPOs, the cuspate shapes of the pargasites, and the absence of intercrystallite deformation. The results, combined with previously reported <em>P–T</em> conditions for the Horoman peridotite complex, indicate that the deformed peridotites and mafic rocks with a layered structure represent temperatures of 1050–1150 °C and pressures of 0.7–1.5 GPa. Our results suggest that a decrease in pressure led to the transition from a melt-free to a melt-bearing system with a consequent change in the deformation mechanism, from dislocation creep in the melt-free system to diffusion creep in the melt-bearing system, with strain localization in the fine-grained melt-rich layers. The change in deformation mechanism is likely to have occurred in the uppermost mantle beneath a mid-ocean ridge, where strong rheological contrasts are controlled by spatial variations in the melt fraction.</p></div>","PeriodicalId":22257,"journal":{"name":"Tectonophysics","volume":null,"pages":null},"PeriodicalIF":2.7,"publicationDate":"2024-09-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142270517","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}