Tectonophysics最新文献

{"title":"Extension rate variations across the South Tibetan rifts – New data from the northern Xainza-Dinggye Graben","authors":"Marie-Luce Chevalier ,&nbsp;Ziqi Fang ,&nbsp;Shenqiang Chen ,&nbsp;Jiawei Pan ,&nbsp;Haibing Li ,&nbsp;Kungang Wu ,&nbsp;Fucai Liu ,&nbsp;Junyi Wang ,&nbsp;Lin Ding","doi":"10.1016/j.tecto.2025.230824","DOIUrl":"10.1016/j.tecto.2025.230824","url":null,"abstract":"<div><div>The active ∼NS-trending rifts in southern Tibet reflect ongoing ∼EW extension alongside ∼NS shortening from the India-Asia collision. Quantifying late Quaternary extension rates is essential to comprehend Tibetan deformation and evolution. Here, we test whether extension rates across the Xainza-Dinggye rift (XDR) are on the same order as those along the Yadong-Gulu rift (YGR), and whether a similar northward increase in extension rate exists along the XDR due to interaction with the dextral Gyaring Co fault to its north as exists along the YGR due to interaction with the dextral Beng Co fault to the north, where rates increase from 0.8 to 1.3 to 3–6 mm/yr from south to north. We use ¹⁰Be cosmogenic dating and topographic surveying at three sites along the northernmost XDR, where geomorphic surfaces are vertically offset by several normal faults bounding the western side of the graben. Our results suggest extension rates &lt;1 mm/yr, i.e., much smaller than those across the YGR, except where surfaces are younger than the Last Glacial Maximum (LGM). This suggests a post-LGM rate acceleration following glacier melting and post-glacial rebound due to fault unloading. Therefore, we may need to reconsider the previous assumption of a constant extension rate of 1.3 mm/yr across each of the seven main rifts yielding a total extension rate of 9 ± 2 mm/yr across southern Tibet. We infer that only the larger and more continuous rifts may absorb significant horizontal extension, compared to smaller rifts which may absorb less. Importantly, that extension rates do not increase northwards along the XDR may be due to its particular orientation perpendicular to the Main Frontal Thrust (MFT), compared to other rifts that are more oblique to it. This reinforces earlier inferences that the rifts are related to divergent, orthogonal thrusting along the curved Himalayan MFT.</div></div>","PeriodicalId":22257,"journal":{"name":"Tectonophysics","volume":"910 ","pages":"Article 230824"},"PeriodicalIF":2.7,"publicationDate":"2025-06-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144331048","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":"Imaging the subsurface location of a hidden fault using autocorrelations of ambient seismic noise recorded by a dense linear seismic array","authors":"Chunhua Shi ,&nbsp;Jiafu Hu ,&nbsp;Hengchu Peng ,&nbsp;Haiyan Yang ,&nbsp;Hong Zhao ,&nbsp;Zhaoli Zhu ,&nbsp;Wei Jia ,&nbsp;José Badal","doi":"10.1016/j.tecto.2025.230821","DOIUrl":"10.1016/j.tecto.2025.230821","url":null,"abstract":"<div><div>Ambient noise autocorrelations functions (ACFs) can elucidate the body-wave reflectivity of the local structure beneath single seismic stations without the need for active sources or earthquakes. However, the large-amplitude signal of the near-zero-lag time in the ACF can interfere with the target reflection(s), thereby hindering the ability to determine the precise location of hidden faults in shallow sediments. In this study, a ∼ 1.2-km-long dense linear seismic array consisting of 30 three-component geophones was deployed orthogonal to the Puqian–Qinglan Fault in Hainan province, China, to image the shallow structure around the fault. Using three components of the noise records, we calculate the ACFs beneath single stations and then subtract the average source time function from the individual ACFs to obtain the body-wave reflectivity section. We then convert the zero-offset reflectivity from the time domain to the depth domain using a constant S-wave velocity of 200 m/s. We also analyse the zero-offset reflectivity by stacking the cross-correlation functions of nearby traces originating from virtual source gathers. The results reveal that the depth to basement increases suddenly from ∼60 m to ∼110 m at ∼360 m profile distance, which we ascribe to offset on the Puqian–Qinglan Fault. This conclusion is verified by an engineering geological study, thereby demonstrating that the ambient noise technique used here may be particularly useful for imaging the near-surface basement structure.</div></div>","PeriodicalId":22257,"journal":{"name":"Tectonophysics","volume":"910 ","pages":"Article 230821"},"PeriodicalIF":2.7,"publicationDate":"2025-06-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144240495","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":"Small-scale heterogeneities near the upper and lower mantle boundary beneath subduction zones","authors":"Satoshi Kaneshima","doi":"10.1016/j.tecto.2025.230820","DOIUrl":"10.1016/j.tecto.2025.230820","url":null,"abstract":"<div><div>Small-scale compositional heterogeneity near the upper and lower mantle boundary below circum-Pacific subduction zones is investigated. We array-process seismograms of deep earthquakes recorded by large-aperture seismic networks at western US, Japan, and Alaska with the aim of examining anomalous signals in the P coda until about 35 s after direct P wave. The signals arrive from the directions close to the direct P wave. The signal amplitudes decay with delay time after the direct P wave and the decay feature apparently depends on focal depth. The signals most likely arise from S-to-P and P-to-P scattering within the lower and/or upper mantle around the foci. We show by applying a stochastic scattering theory for randomly heterogeneous media that the observations are matched well by density and rigidity anomalies of spatial scale on the order of 10 km, which diminish below about 700 km depth. The observations are matched if the rigidity anomaly is of the same sign and three to four times as large as the density anomaly. These properties of the scattering objects could be consistent with the predicted elastic anomalies of basalt near the upper and lower mantle boundary relative to the surrounding mantle of pyrolytic composition. The estimated weak degree of density heterogeneity, on the order of 0.01 to 0.1 %, may reflect sparse distribution of basaltic material of 10 km scale in the uppermost 100 km of the lower mantle possibly resulting from the significantly smaller density of basalt than the surrounding rock.</div></div>","PeriodicalId":22257,"journal":{"name":"Tectonophysics","volume":"910 ","pages":"Article 230820"},"PeriodicalIF":2.7,"publicationDate":"2025-06-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144307943","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":"Fault interactions and subsurface deformation in the Mexicali Valley: Implications for seismic hazard assessment at the México-USA border","authors":"Cristian A. Gallegos-Castillo ,&nbsp;Mario González-Escobar ,&nbsp;Jaime A. Reyes-López ,&nbsp;Joann M. Stock ,&nbsp;Sergio M. Arregui-Ojeda ,&nbsp;Carlos Simón Reyes-Martínez ,&nbsp;Edgar A. Mastache-Román","doi":"10.1016/j.tecto.2025.230803","DOIUrl":"10.1016/j.tecto.2025.230803","url":null,"abstract":"<div><div>This study investigates both previously known and unidentified subsurface deformation structures in the northwesternmost sector of the Mexicali Valley, México, near the international border with the USA. Several subsurface structures, including the Michoacán fault, have been identified between the Imperial-Laguna Salada fault zones by analyzing seismic reflection profiles, and their locations have been correlated with seismicity patterns. This study highlights the northward extension of the Michoacán fault beyond the border with the United States. While the trace of this fault has been reported elsewhere, some evidence has associated the existing deformation with a distinct, previously unknown structure; herein, named the Progreso Fault. The Dixieland Fault (USA) is not observed in México; however, the interaction of these faults plays a significant role in the regional seismic activity. Slip is distributed throughout the sector and is not concentrated on specific faults such as the Michoacán or Imperial. Faults with different orientations located between the Michoacán and Imperial Fault zones represent the potential northern limit of the Cerro Prieto Pull-Apart Basin. Additionally, several sub-basins have been identified in the study area. Although the two-dimensional seismic imagery used in this study does not allow for slip rate calculations on the faults, the observed structures provide valuable information about displacement and subsurface deformation in the region. The structures reported here contribute to the SCEC Community Fault Model (CFM), which integrates seismic reflection and other geological and geophysical data to define fault geometries. The CFM serves as a key input for physics-based fault system modeling and probabilistic seismic hazard assessments, including the Uniform California Earthquake Rupture Forecast (UCERF3). Consequently, the findings will aid in understanding regional fault interactions, providing essential constraints for future research and facilitating a better understanding of seismic hazards in the México-USA border region.</div></div>","PeriodicalId":22257,"journal":{"name":"Tectonophysics","volume":"910 ","pages":"Article 230803"},"PeriodicalIF":2.7,"publicationDate":"2025-06-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144261646","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":"Present-day stress field in SE margin of Tibetan plateau by comprehensive updated earthquake focal mechanisms and its tectonic implications","authors":"Jianhui Tian ,&nbsp;Yuan Gao","doi":"10.1016/j.tecto.2025.230817","DOIUrl":"10.1016/j.tecto.2025.230817","url":null,"abstract":"<div><div>The Sichuan-Yunnan region of the SE and E margin of the Tibetan Plateau, situated at the transitional nexus between the seismically-active and intensely-deformed Tibetan Plateau and the tectonically stable Yangtze block with comparatively low seismicity, has experienced substantial tectonic transformations during the Quaternary. Given the pronounced seismicity, there is an escalating imperative for an accurate and refined distribution of the stress field in the region. To unravel the contemporary stress state within major active blocks and along active faults in the study area, the tectonic stress field is calculated by comprehensive updated earthquake focal mechanisms catalogue. The tectonic stress field in Sichuan-Yunnan region exhibits significant lateral variations in direction and stress pattern. The directions of the maximum and minimum principal stress in the north are nearly E-W compressions and N-S tensions, respectively. Conversely, in the south, there is a discernible clockwise rotation trend from east to west. Localized normal faulting stress regimes are observed in the middle section of Xianshuihe fault and SW side of Litang fault. The extensional environment of the former may be attributed to the tectonic activities such as block translation, clockwise rotation and the strike variation of the Xianshuihe fault from NW-SW to NNW-SSE. The latter may be related to the extensional structures, rift basins and the normal fault movements in the crust formed by the detachment of the plates and delamination of the mountain roots at the end of Triassic. We also found that the stress field under the large faults, such as Longmenshan fault, Red River fault, Xiaojiang fault and Lijiang-Xiaojinhe fault, show segmented variation. The findings yield invaluable insights into the intricate dynamics of tectonic deformation along the SE and E margin of the Tibetan Plateau.</div></div>","PeriodicalId":22257,"journal":{"name":"Tectonophysics","volume":"910 ","pages":"Article 230817"},"PeriodicalIF":2.7,"publicationDate":"2025-05-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144230097","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":"Southernmost Kerguelen Plateau – Not a continental fragment","authors":"Wilfried Jokat ,&nbsp;Tabea Altenbernd-Lang ,&nbsp;Karsten Gohl ,&nbsp;German L. Leitchenkov ,&nbsp;Hannes Eisermann","doi":"10.1016/j.tecto.2025.230804","DOIUrl":"10.1016/j.tecto.2025.230804","url":null,"abstract":"<div><div>Most models on the early continental drift of the Indian continent from Antarctica are guided by the existence of microcontinents that are supposed to be located beneath Elan Bank and the Southern Kerguelen Plateau in the Enderby Basin off East Antarctica. Two deep seismic lines were acquired to test these ideas by investigating the distribution of oceanic and continental crust in the Enderby Basin. In this contribution, we discuss the results of the eastern profile which images the crustal structure of the southernmost Kerguelen Plateau. The new deep seismic data show that the seismic velocity structure of the southernmost Kerguelen Plateau is different to that of extended continental crust but similar to other igneous oceanic plateaus worldwide. At the northern end of the profile, the Moho discontinuity lies at a depth below sea level of approximately 25 km. The position of the East Antarctic continent-ocean boundary is located close to its continental shelf edge. The maximum thickness of the East Antarctic transitional crust, at the southern termination of our line, is 22 km. Extrapolating our seismic reflection and refraction results show that the oceanic crust at 50° - 90°E in the Enderby Basin and Princess Elizabeth Trough formed whilst in receipt of excess melt from the Kerguelen plume around magnetic chron M4n causing a northward thickening of the oceanic crust since 130 Ma. These results strongly support a one-phase model for the drift of the Indian plate.</div></div>","PeriodicalId":22257,"journal":{"name":"Tectonophysics","volume":"910 ","pages":"Article 230804"},"PeriodicalIF":2.7,"publicationDate":"2025-05-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144194969","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 2023 Mw 7.8 Kahramanmaraş earthquake rupture increases potential failure along the northern Dead Sea Fault","authors":"Mustapha Meghraoui ,&nbsp;Ziyadin Cakir ,&nbsp;Jugurtha Kariche ,&nbsp;Renaud Toussaint ,&nbsp;Floriane Provost ,&nbsp;Volkan Karabacak ,&nbsp;Reda Sbeinati ,&nbsp;Erhan Altunel ,&nbsp;Tony Nemer","doi":"10.1016/j.tecto.2025.230799","DOIUrl":"10.1016/j.tecto.2025.230799","url":null,"abstract":"<div><div>The 6 February 2023 earthquake sequence along the East Anatolian Fault (EAF, Mw 7.8) and Çardak fault (CF, Mw 7.6) in southern Turkiye reveals the importance of seismic gaps and fault segments interaction. Both large earthquakes show shallow hypocentres (&lt;15 km), strike-slip mechanisms, with the N<em>E</em>-SW trending Golbaşi-Kahramanmaraş-Karasu fault segments reaching ∼350 km and the E-W trending Çardak fault ∼150 km. Field investigations of surface ruptures, aided by Sentinel 2 image correlation, document the coseismic slip distribution, reaching 8 m on the Pazarcik segment and 4.1 m on the Kirikhan segment. Prior to the recent seismic sequence, our field investigations included the SW segments of the EAF and northern Dead Sea Fault (DSF). Detailed fault mapping was conducted from 2003 to 2007 along the EAF fault from Golbaşi to Antakia and along the DSF from the Ghab Basin to the Amik Basin and the intersection with the EAF. According to contemporaneous historical accounts, the 29 November 1114 earthquake that severely affected Antakia, Marash (Kahramanmaraş), Adiyaman and Urfa (Şanlurfa) causing 40,000 victims, may represent the predecessor to the 2023 Mw 7.8 earthquake. A possible evidence of fault interaction between the EAF and Dead Sea Fault (DSF) is shown by the southward migration of large historical earthquakes from the major 1114 CE seismic event on the SW EAF to the 1138 CE, 1156, 1170, and 1202 large earthquake sequences on the northern segments of DSF. The modelling of the seismic slip deficit and stress transfer illustrates the significant seismic hazard with the potential for a failure increase and a ∼ 21 year-time clustering of major events along the northern DSF segments.</div></div>","PeriodicalId":22257,"journal":{"name":"Tectonophysics","volume":"910 ","pages":"Article 230799"},"PeriodicalIF":2.7,"publicationDate":"2025-05-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144178728","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":"Seismicity, faulting, and the magmatic fluid influence: Insights from the 2023 ML5.4 earthquake sequence in the Beibu Gulf","authors":"Xiaoling Xie ,&nbsp;Jiangnan Lin ,&nbsp;Yiming Liu ,&nbsp;Hui Zhang ,&nbsp;Huilin Wang","doi":"10.1016/j.tecto.2025.230800","DOIUrl":"10.1016/j.tecto.2025.230800","url":null,"abstract":"<div><div>The Beibu Gulf and its surroundings represent a significant intraplate seismic zone in the northwest of the South China Sea. Historically, this region has experienced at least 15 M &gt; 5 earthquakes and 4 M &gt; 6 events, including a devastating M7.5 earthquake in 1605. Despite the serious earthquake risk in this seismic zone, few studies have focused on the moderate to strong earthquake sequences, resulting in unclear seismic structures, mechanisms, and triggers. This study investigates the 2023 Beibu Gulf (BBG) earthquake sequence (M_L5.4) using four months of waveform data from 51 broadband stations. We detected one foreshock and 73 aftershocks using template matching techniques, relocated the earthquake sequence with the HypoDD method, and inverted focal mechanisms for 12 M &gt; 1.5 earthquakes. The results indicate that the 2023 BBG earthquake sequence forms a belt in the NWW-SEE direction, extending laterally ∼5.0 km and vertically ∼1.5 km, with a dip angle of ∼52° toward the NNE. Most foreshocks and aftershocks exhibit source mechanisms similar to the mainshock, corresponding with the NWW-trending Wei-2 Fault (F1). The principal stress direction in the source region is NW-SE, intersecting obliquely with the F1, resulting in the right-lateral strike-slip faulting of the 2023 BBG earthquake sequence. Ambient noise tomography reveals a deep columnar low-velocity zone beneath the sequence, suggesting a possible relationship with magmatic-hydrothermal fluids from the Hainan mantle plume. By integrating seismic activity characteristics and geological data, we conclude that deep hydrothermal fluids and fault structures or weak zones are the primary driving factors of seismicity in this region.</div></div>","PeriodicalId":22257,"journal":{"name":"Tectonophysics","volume":"910 ","pages":"Article 230800"},"PeriodicalIF":2.7,"publicationDate":"2025-05-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144170647","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":"Late Pleistocene thrust tectonics in the north Peruvian forearc revealed by Terrestrial Cosmogenic Nuclides surface exposure dating, field structural data and seismic profiles","authors":"Andréa Peuzin ,&nbsp;Marianne Saillard ,&nbsp;Nicolas Espurt ,&nbsp;Régis Braucher ,&nbsp;Marc Régnier ,&nbsp;Guillaume Duclaux ,&nbsp;Laurence Audin ,&nbsp;Adriana Lemgruber-Traby ,&nbsp;Olivier Bellier ,&nbsp;Jean-Claude Hippolyte ,&nbsp;Ysabel Calderon","doi":"10.1016/j.tecto.2025.230798","DOIUrl":"10.1016/j.tecto.2025.230798","url":null,"abstract":"<div><div>Precise dating of geomorphic markers that are subject to thrust-related deformation, such as alluvial fan surface are crucial for quantifying forearc deformation, especially in a context of weak interseismic coupling on the subduction interface as in northern Peru. In this study, we document the late Pleistocene tectonic history of the Amotape massif, which is a prominent basement relief in the northern Peruvian forearc. To achieve this, we combine a morphometric analysis and Terrestrial Cosmogenic Nuclides (TCNs) surface exposure dating of alluvial fan surface with subsurface structural data. TCNs (¹⁰Be and ²⁶Al) surface exposure ages of alluvial fan surfaces on the northwestern flank of the massif range from 35.1 ± 1.1 ka to 59.3 ± 2.1 ka for ¹⁰Be and from 27.3 ± 2.0 ka to 48.9 ± 2.5 ka for ²⁶Al. Both cosmogenic nuclides provide consistent results. We calculated a mean weighted age of 39.0 ± 0.3 ka for an alluvial fan that is offset by a major NW-verging thrust. Our results provide an estimated slip rate of 1.15 ± 0.46 m/ka along the Amotape thrust front since the late Pleistocene. The surface deformation along the Amotape thrust front correlates with the top portion of a deep-seated contractional wedge involving the crustal basement, according to subsurface structural data and regional seismicity. This integrated analysis demonstrates active shortening in the onshore crustal basement of the northern Peruvian forearc where no active thrust reaching the surface has been described before.</div></div>","PeriodicalId":22257,"journal":{"name":"Tectonophysics","volume":"910 ","pages":"Article 230798"},"PeriodicalIF":2.7,"publicationDate":"2025-05-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144230096","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":"Strong crustal heterogeneity of the Xianshuihe-Anninghe-Zemuhe fault system and its vicinity revealed by velocity and azimuthal anisotropy structures","authors":"Shaolin Liu ,&nbsp;Kailin Sun ,&nbsp;Dinghui Yang ,&nbsp;Mengyang Li ,&nbsp;Hanjie Song ,&nbsp;Wenshuai Wang ,&nbsp;Kai Chang","doi":"10.1016/j.tecto.2025.230801","DOIUrl":"10.1016/j.tecto.2025.230801","url":null,"abstract":"<div><div>The Xianshuihe-Anninghe-Zemuhe (XAZ) fault system acts as the eastern boundary of the Chuan-Dian block, and it separates the Chuan-Dian block from the Songpan-Ganzi block (SGB) and the Yangtze block. Due to the SE-ward expansion of the Tibetan Plateau, strong crustal deformation has occurred in the XAZ fault system and its vicinity. Although many studies on crustal deformation have been conducted in the past twenty years, some key issues remain poorly resolved. To further investigate crustal deformation, we perform P-wave anisotropy tomography using an eikonal equation-based tomography method, and obtain high resolution 3D P-wave velocity and azimuthal anisotropy images beneath the XAZ fault system and its vicinity. Our tomographic results show two separate strong low-velocity bodies in the mid-lower crust of the XAZ fault system. In addition, our results do not present a consistent anisotropy pattern with fast velocity directions parallel to the strike of the XAZ fault system. Based on these features, we conclude that mid-lower crustal flow, which is employed to explain the expansion of the Tibetan Plateau, does not occur along the XAZ fault system. Furthermore, our tomographic results display a high-velocity body in the upper crust below the SGB, and the high-velocity body connects with the high-velocity anomaly beneath the Sichuan basin (SCB). According to these features, we suggest that the Yangtze crystalline basement penetrates into the eastern Tibetan Plateau across the Longmenshan fault.</div></div>","PeriodicalId":22257,"journal":{"name":"Tectonophysics","volume":"909 ","pages":"Article 230801"},"PeriodicalIF":2.7,"publicationDate":"2025-05-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144167991","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}