Pub Date : 2025-11-04DOI: 10.1016/j.tecto.2025.230985
Fengxue Zhang , Yu Li , Yiping Chen
This study explores the velocity structure of the 2025 Mw7.7 Myanmar earthquake source region using seismic wave traveltime reciprocity tomography, a method that leverages the reciprocal relationship between sources and receivers to address the challenge of sparse station coverage. This inversion resolves robust velocity anomalies and remains generally stable with respect to the changes in the spatial extent of the study area. Tomographic results reveal a prominent north-south low-velocity zone that extends along the north-south trending Sagaing Fault, highlighting its role as the primary rupture zone. To the east of the fault, a broad high-velocity anomaly likely marks the steeply eastward-subducting Indian Plate beneath the Shan Plateau, whereas to the west, a localized high-velocity feature is consistent with a near-horizontal slab morphology beneath the Myanmar Central Basin. These findings provide new constraints on the deep structure and geodynamic processes beneath Myanmar.
{"title":"Velocity structure of the 2025 Mw7.7 Myanmar earthquake source region: Insights from traveltime reciprocity tomography","authors":"Fengxue Zhang , Yu Li , Yiping Chen","doi":"10.1016/j.tecto.2025.230985","DOIUrl":"10.1016/j.tecto.2025.230985","url":null,"abstract":"<div><div>This study explores the velocity structure of the 2025 Mw7.7 Myanmar earthquake source region using seismic wave traveltime reciprocity tomography, a method that leverages the reciprocal relationship between sources and receivers to address the challenge of sparse station coverage. This inversion resolves robust velocity anomalies and remains generally stable with respect to the changes in the spatial extent of the study area. Tomographic results reveal a prominent north-south low-velocity zone that extends along the north-south trending Sagaing Fault, highlighting its role as the primary rupture zone. To the east of the fault, a broad high-velocity anomaly likely marks the steeply eastward-subducting Indian Plate beneath the Shan Plateau, whereas to the west, a localized high-velocity feature is consistent with a near-horizontal slab morphology beneath the Myanmar Central Basin. These findings provide new constraints on the deep structure and geodynamic processes beneath Myanmar.</div></div>","PeriodicalId":22257,"journal":{"name":"Tectonophysics","volume":"918 ","pages":"Article 230985"},"PeriodicalIF":2.6,"publicationDate":"2025-11-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145434701","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}
The role of the en echelon Karakorum-Jiali fault zone (KJFZ) in accommodating eastward extrusion of the Tibetan Plateau remains a subject of ongoing debate. To clarify the present-day strain accumulation along its eastern section (encompassing the Gyaring Co, Beng Co, and Jiali faults), we integrated Sentinel-1 InSAR and GNSS velocities to derive a comprehensive three-dimensional crustal deformation field. Our analysis revealed distributed dextral shear across the Lhasa terrane east of the Yadong-Gulu rift, a sharp contrast to the concentrated shear west of this rift. Both the Beng Co fault and the Gyaring Co fault exhibit a dextral slip rate of ∼3 mm/yr and extend beyond their previously mapped traces. Quantifying the slip rate of the Jiali fault proved challenging due to the smooth deformation gradient across it; the shear strain is primarily concentrated to its south along the western segment (from Nagqu to Xiama), yet shifts to the north along the central segments (from Jiali to Yigong). This spatial variation suggests that the Bianba Lhorong fault to the north is likely the easternmost strand of the KJFZ. Furthermore, we identified focused uplift of 2–3 mm/yr along the central segments of the Jiali fault, potentially driven by reverse faulting and/or deglaciation unloading. Such a present-day strain partitioning pattern indicates that the Tibetan crust's eastward-increasing lateral extrusion is collectively accommodated by the approximately E-W trending dextral strike-slip active faults situated between the KJFZ and the Himalayan arc, implying lower slip rate than the previously proposed 10–20 mm/yr for the KJFZ.
{"title":"Deformation pattern and slip rate of the Karakorum-Jiali Fault Zone in Southeastern Tibet from Sentinel-1 InSAR","authors":"Yunfeng Tian , Jing Liu-Zeng , Wanpeng Feng , Jingfa Zhang , Baoqi Ma , Wenliang Jiang","doi":"10.1016/j.tecto.2025.230976","DOIUrl":"10.1016/j.tecto.2025.230976","url":null,"abstract":"<div><div>The role of the en echelon Karakorum-Jiali fault zone (KJFZ) in accommodating eastward extrusion of the Tibetan Plateau remains a subject of ongoing debate. To clarify the present-day strain accumulation along its eastern section (encompassing the Gyaring Co, Beng Co, and Jiali faults), we integrated Sentinel-1 InSAR and GNSS velocities to derive a comprehensive three-dimensional crustal deformation field. Our analysis revealed distributed dextral shear across the Lhasa terrane east of the Yadong-Gulu rift, a sharp contrast to the concentrated shear west of this rift. Both the Beng Co fault and the Gyaring Co fault exhibit a dextral slip rate of ∼3 mm/yr and extend beyond their previously mapped traces. Quantifying the slip rate of the Jiali fault proved challenging due to the smooth deformation gradient across it; the shear strain is primarily concentrated to its south along the western segment (from Nagqu to Xiama), yet shifts to the north along the central segments (from Jiali to Yigong). This spatial variation suggests that the Bianba Lhorong fault to the north is likely the easternmost strand of the KJFZ. Furthermore, we identified focused uplift of 2–3 mm/yr along the central segments of the Jiali fault, potentially driven by reverse faulting and/or deglaciation unloading. Such a present-day strain partitioning pattern indicates that the Tibetan crust's eastward-increasing lateral extrusion is collectively accommodated by the approximately <em>E</em>-W trending dextral strike-slip active faults situated between the KJFZ and the Himalayan arc, implying lower slip rate than the previously proposed 10–20 mm/yr for the KJFZ.</div></div>","PeriodicalId":22257,"journal":{"name":"Tectonophysics","volume":"918 ","pages":"Article 230976"},"PeriodicalIF":2.6,"publicationDate":"2025-11-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145427977","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}
Pub Date : 2025-11-02DOI: 10.1016/j.tecto.2025.230977
Ying Zhang , Hao Hu , Walter D. Mooney
The Fiji-Lau Basin-Tonga-Samoa region, situated at a complex tectonic junction involving subduction, back-arc spreading, and mantle plume activity, provides a natural laboratory for investigating crustal growth processes at convergent margins, and enhances regional seismic hazards assessments. We present estimates of crustal thickness variations and Vp/Vs ratios derived from P-wave receiver functions and H-κ stacking across 46 broadband seismic stations from multiple networks. Our results reveal a mean crustal thickness of ∼17.8 km and an average Vp/Vs ratio of 1.84, consistent with an intermediate to mafic crustal composition. Crustal thickness varies significantly across the region, with the thickest crust (∼30 km) beneath northern Fiji, a remnant island arc formed during Eocene-Miocene subduction. In comparison, the thinnest (∼6 km) is observed in the actively spreading Lau Basin. Intermediate thicknesses (19–25 km) are observed along the Lau and Tonga Ridges. In the Samoa Islands, crustal thickness increases eastward from 16 km to 25 km, paired with declining Vp/Vs ratios (1.9 to 1.6), suggesting a compositional transition from subduction-related magmatism to more differentiated felsic intraplate magmatism associated with the Samoan hotspot. Although the thinner crust across the island arc systems lacks sufficient volume to form continental crust without post-accretionary thickening, the presence of thicker crust (23–30 km) beneath parts of the region may represent incipient juvenile continental crustal formation.
{"title":"Crustal structure of the Fiji-Lau Basin-Tonga-Samoa region from receiver functions","authors":"Ying Zhang , Hao Hu , Walter D. Mooney","doi":"10.1016/j.tecto.2025.230977","DOIUrl":"10.1016/j.tecto.2025.230977","url":null,"abstract":"<div><div>The Fiji-Lau Basin-Tonga-Samoa region, situated at a complex tectonic junction involving subduction, back-arc spreading, and mantle plume activity, provides a natural laboratory for investigating crustal growth processes at convergent margins, and enhances regional seismic hazards assessments. We present estimates of crustal thickness variations and Vp/Vs ratios derived from P-wave receiver functions and H-κ stacking across 46 broadband seismic stations from multiple networks. Our results reveal a mean crustal thickness of ∼17.8 km and an average Vp/Vs ratio of 1.84, consistent with an intermediate to mafic crustal composition. Crustal thickness varies significantly across the region, with the thickest crust (∼30 km) beneath northern Fiji, a remnant island arc formed during Eocene-Miocene subduction. In comparison, the thinnest (∼6 km) is observed in the actively spreading Lau Basin. Intermediate thicknesses (19–25 km) are observed along the Lau and Tonga Ridges. In the Samoa Islands, crustal thickness increases eastward from 16 km to 25 km, paired with declining Vp/Vs ratios (1.9 to 1.6), suggesting a compositional transition from subduction-related magmatism to more differentiated felsic intraplate magmatism associated with the Samoan hotspot. Although the thinner crust across the island arc systems lacks sufficient volume to form continental crust without post-accretionary thickening, the presence of thicker crust (23–30 km) beneath parts of the region may represent incipient juvenile continental crustal formation.</div></div>","PeriodicalId":22257,"journal":{"name":"Tectonophysics","volume":"918 ","pages":"Article 230977"},"PeriodicalIF":2.6,"publicationDate":"2025-11-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145427978","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}
Pub Date : 2025-11-01DOI: 10.1016/j.tecto.2025.230979
Laurent Bollinger , Emile A. Okal
The 1934 Bihar-Nepal earthquake is the largest instrumental earthquake to strike Nepal. However, its moment magnitude is still associated with considerable uncertainty in the literature, with a wide range of values between 8.0 ± 0.3 and as high as 8.4. In this paper we re-evaluate its seismic moment using teleseismic surface wave records from 6 stations. A total of 10 independent measurements lead to a seismic moment of 3.8 × 1021 N.m (Mw = 8.3 ± 0.1), releasing more than 4 times the seismic moment of the 2015 Gorkha earthquake.
Given this seismic moment release, we consider several rupture scenarios with different length-width-slip estimates for the mainshock. We compare them with slip estimates derived from field observations and show that the average slip is likely to have been between 8 and 16 m, a value significantly larger than previous estimates. We compare the dimensions obtained with those of other intercontinental thrust earthquakes. The results reduce the uncertainties associated with the assessment of the deficit of the seismic moment accumulated since the great earthquakes of the medieval period in Nepal.
{"title":"A quantitative reassessment of the 1934 Bihar-Nepal earthquake and its seismotectonic implications","authors":"Laurent Bollinger , Emile A. Okal","doi":"10.1016/j.tecto.2025.230979","DOIUrl":"10.1016/j.tecto.2025.230979","url":null,"abstract":"<div><div>The 1934 Bihar-Nepal earthquake is the largest instrumental earthquake to strike Nepal. However, its moment magnitude is still associated with considerable uncertainty in the literature, with a wide range of values between 8.0 ± 0.3 and as high as 8.4. In this paper we re-evaluate its seismic moment using teleseismic surface wave records from 6 stations. A total of 10 independent measurements lead to a seismic moment of 3.8 × 10<sup>21</sup> N.m (M<sub>w</sub> = 8.3 ± 0.1), releasing more than 4 times the seismic moment of the 2015 Gorkha earthquake.</div><div>Given this seismic moment release, we consider several rupture scenarios with different length-width-slip estimates for the mainshock. We compare them with slip estimates derived from field observations and show that the average slip is likely to have been between 8 and 16 m, a value significantly larger than previous estimates. We compare the dimensions obtained with those of other intercontinental thrust earthquakes. The results reduce the uncertainties associated with the assessment of the deficit of the seismic moment accumulated since the great earthquakes of the medieval period in Nepal.</div></div>","PeriodicalId":22257,"journal":{"name":"Tectonophysics","volume":"918 ","pages":"Article 230979"},"PeriodicalIF":2.6,"publicationDate":"2025-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145424076","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}
Pub Date : 2025-10-31DOI: 10.1016/j.tecto.2025.230975
Ping Wang , Haijian Lu , Liang Duan , Xuxuan Ma , Yihu Zhang , Wang Li
The Late Cretaceous magmatic rocks, widely distributed along the Bangong-Nujiang Suture Zone (BNSZ), not only records large-scale crust-mantle interactions, but also contains characteristic fingerprints of deep geodynamic processes. However, the formation regime is still controversial, with proposed mechanisms including lithospheric delamination, the rollback of the Neo-Tethys Ocean, and the subduction of the Bangong-Nujiang Ocean. To address this issue, we conducted zircon UPb dating, in situ Hf isotope analysis, and whole-rock major and trace element compositions on the Late Cretaceous volcanic rocks in the Lunpola Basin, central Tibet. Geochronological results indicate that they crystallized primarily at ∼80 Ma, which was followed by a ∼ 65 Ma pulse. These volcanic rocks exhibit high-K compositions (K₂O/Na₂O = 1.8–55.8), marked by enrichment in Rb, Th, Pb, and light rare earth elements (LREEs), coupled with depletion in Nb, Ta, and Ti—a geochemical signature diagnostic for subduction-related magmatism. The broad range of zircon εHf(t) values (−15.49 to +15.51) provides robust evidence for contributions from Qiangtang ancient continent crust to the formation of the (ultra) potassic rocks. Given the widespread distribution of coeval (∼80 Ma) magmatic rocks along the BNSZ and geophysical data, we propose that the petrogenesis of the Late Cretaceous potassic rocks originated from southward subduction of the Qiangtang terrane beneath the Lhasa terrane. This study not only proposes a new tectonic model for the nature of the Lhasa-Qiangtang collision but also highlights the vital role of intracontinental subduction in producing post-collisional potassic-ultrapotassic magmatism.
{"title":"Late Cretaceous intracontinental subduction along the Bangong-Nujiang Suture Zone: evidence from the K-rich magmatism in the Lunpola Basin, central Tibetan Plateau","authors":"Ping Wang , Haijian Lu , Liang Duan , Xuxuan Ma , Yihu Zhang , Wang Li","doi":"10.1016/j.tecto.2025.230975","DOIUrl":"10.1016/j.tecto.2025.230975","url":null,"abstract":"<div><div>The Late Cretaceous magmatic rocks, widely distributed along the Bangong-Nujiang Suture Zone (BNSZ), not only records large-scale crust-mantle interactions, but also contains characteristic fingerprints of deep geodynamic processes. However, the formation regime is still controversial, with proposed mechanisms including lithospheric delamination, the rollback of the Neo-Tethys Ocean, and the subduction of the Bangong-Nujiang Ocean. To address this issue, we conducted zircon U<img>Pb dating, in situ Hf isotope analysis, and whole-rock major and trace element compositions on the Late Cretaceous volcanic rocks in the Lunpola Basin, central Tibet. Geochronological results indicate that they crystallized primarily at ∼80 Ma, which was followed by a ∼ 65 Ma pulse. These volcanic rocks exhibit high-K compositions (K₂O/Na₂O = 1.8–55.8), marked by enrichment in Rb, Th, Pb, and light rare earth elements (LREEs), coupled with depletion in Nb, Ta, and Ti—a geochemical signature diagnostic for subduction-related magmatism. The broad range of zircon ε<sub>Hf</sub>(<em>t</em>) values (−15.49 to +15.51) provides robust evidence for contributions from Qiangtang ancient continent crust to the formation of the (ultra) potassic rocks. Given the widespread distribution of coeval (∼80 Ma) magmatic rocks along the BNSZ and geophysical data, we propose that the petrogenesis of the Late Cretaceous potassic rocks originated from southward subduction of the Qiangtang terrane beneath the Lhasa terrane. This study not only proposes a new tectonic model for the nature of the Lhasa-Qiangtang collision but also highlights the vital role of intracontinental subduction in producing post-collisional potassic-ultrapotassic magmatism.</div></div>","PeriodicalId":22257,"journal":{"name":"Tectonophysics","volume":"918 ","pages":"Article 230975"},"PeriodicalIF":2.6,"publicationDate":"2025-10-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145412221","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}
Pub Date : 2025-10-30DOI: 10.1016/j.tecto.2025.230973
Sheng Zhang , Nian Yu , Xin Li , Wenxin Kong , Zikun Zhou , Tianyang Li
The present-day tectonic deformation in the Eastern Sichuan Fold-Thrust (ESFTB) far away from plate boundaries is relatively weak, but several moderate to strong earthquakes have occurred in this region during the past decades. To investigate the deep structure and seismogenic environment of this area, a dense broadband magnetotelluric (MT) array were deployed to obtain a three-dimensional (3-D) image of the crustal electrical conductivity structure across the ESFTB. Our resistivity model reveals significant differences in both the depth extent and magnitude of the low-resistivity anomalies in the upper-middle crust on either side of the Qiyao-Jinfoshan Fault (QY-JFF), which has been considered as the boundary between thin-skinned and thick-skinned tectonics. Beneath the QY-JFF, a notable high-resistivity body is imaged and likely reflects the cooled basaltic intrusions associated with the Permain Emeishan volcanism. Given the tectonic context, we prefer to interpret the low-resistivity anomalies as aqueous fluids mainly generated by metamorphic dehydration of the fluid-rich detachment layers, and attribute the differences on either side of the QY-JFF to differing degrees of compressive folding occurred during the early Mesozoic. Most earthquakes along the Fangdoushan Fault (FDSF) are concentrated in a relatively low resistive region that is sandwiched between conductive zones of fluid-rich rock, implying that deep fluid migration into the upper crust may have contributed to triggering earthquakes in this area. Taking into account that these earthquakes are in close proximity to the Yangtze River, the downward infiltration of surface water could also be a potential source of fluids and act as a triggering mechanism for earthquakes.
{"title":"Crustal structure and seismogenic environment of the Eastern Sichuan Fold-Thrust Belt in South China: Insights from a dense magnetotelluric array","authors":"Sheng Zhang , Nian Yu , Xin Li , Wenxin Kong , Zikun Zhou , Tianyang Li","doi":"10.1016/j.tecto.2025.230973","DOIUrl":"10.1016/j.tecto.2025.230973","url":null,"abstract":"<div><div>The present-day tectonic deformation in the Eastern Sichuan Fold-Thrust (ESFTB) far away from plate boundaries is relatively weak, but several moderate to strong earthquakes have occurred in this region during the past decades. To investigate the deep structure and seismogenic environment of this area, a dense broadband magnetotelluric (MT) array were deployed to obtain a three-dimensional (3-D) image of the crustal electrical conductivity structure across the ESFTB. Our resistivity model reveals significant differences in both the depth extent and magnitude of the low-resistivity anomalies in the upper-middle crust on either side of the Qiyao-Jinfoshan Fault (QY-JFF), which has been considered as the boundary between thin-skinned and thick-skinned tectonics. Beneath the QY-JFF, a notable high-resistivity body is imaged and likely reflects the cooled basaltic intrusions associated with the Permain Emeishan volcanism. Given the tectonic context, we prefer to interpret the low-resistivity anomalies as aqueous fluids mainly generated by metamorphic dehydration of the fluid-rich detachment layers, and attribute the differences on either side of the QY-JFF to differing degrees of compressive folding occurred during the early Mesozoic. Most earthquakes along the Fangdoushan Fault (FDSF) are concentrated in a relatively low resistive region that is sandwiched between conductive zones of fluid-rich rock, implying that deep fluid migration into the upper crust may have contributed to triggering earthquakes in this area. Taking into account that these earthquakes are in close proximity to the Yangtze River, the downward infiltration of surface water could also be a potential source of fluids and act as a triggering mechanism for earthquakes.</div></div>","PeriodicalId":22257,"journal":{"name":"Tectonophysics","volume":"918 ","pages":"Article 230973"},"PeriodicalIF":2.6,"publicationDate":"2025-10-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145404639","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}
Pub Date : 2025-10-30DOI: 10.1016/j.tecto.2025.230974
Vincent Soustelle , Emily J. Chin
The peritectic reaction whereby olivine reacts with silica-rich melt to crystallize orthopyroxene occurs in various settings such as mid-ocean ridges, mantle plumes, and subduction zones, thereby modifying upper mantle properties. While many studies have investigated how olivine crystallographic (CPO) and shape-preferred orientations (SPO) evolve during deformation in presence of melt, pyroxene CPO has received less attention, despite orthopyroxene being the second most abundant mantle mineral. Natural examples of synkinematic melt–rock reactions in peridotites often display CPO in reaction products without clear evidence of intracrystalline deformation.
Here, we investigate the evolution of orthopyroxene (enstatite) SPO and CPO in high-pressure, high-temperature olivine + melt deformation experiments. Olivine shows abundant evidence for dislocation creep, with CPO patterns evolving from axial-[010] at shear strains <1 to A-type at shear strains ∼2. In contrast, orthopyroxene develops strong CPO without signs of intracrystalline deformation. Instead, it displays a strong SPO: the long axis coincides with [100] and aligns with the shear direction, while the short axis forms a girdle between [100] and [010]. This correlation indicates that orthopyroxene CPO is governed by its SPO.
We propose that once orthopyroxene crystallizes, the longest facet developing along [001] followed by crystal rotation into the shear direction. Our experiments replicate natural microstructures and CPO observed in melt–rock reacted peridotites, supporting a model where orthopyroxene CPO forms through SPO-controlled rotation during crystallization. This mechanism provides a diagnostic tool to recognize synkinematic melt–rock reactions and to interpret fossil melt pathways in natural peridotites.
{"title":"Shape-preferred orientation induced by melt-rock reaction controls orthopyroxene CPO","authors":"Vincent Soustelle , Emily J. Chin","doi":"10.1016/j.tecto.2025.230974","DOIUrl":"10.1016/j.tecto.2025.230974","url":null,"abstract":"<div><div>The peritectic reaction whereby olivine reacts with silica-rich melt to crystallize orthopyroxene occurs in various settings such as mid-ocean ridges, mantle plumes, and subduction zones, thereby modifying upper mantle properties. While many studies have investigated how olivine crystallographic (CPO) and shape-preferred orientations (SPO) evolve during deformation in presence of melt, pyroxene CPO has received less attention, despite orthopyroxene being the second most abundant mantle mineral. Natural examples of synkinematic melt–rock reactions in peridotites often display CPO in reaction products without clear evidence of intracrystalline deformation.</div><div>Here, we investigate the evolution of orthopyroxene (enstatite) SPO and CPO in high-pressure, high-temperature olivine + melt deformation experiments. Olivine shows abundant evidence for dislocation creep, with CPO patterns evolving from axial-[010] at shear strains <1 to A-type at shear strains ∼2. In contrast, orthopyroxene develops strong CPO without signs of intracrystalline deformation. Instead, it displays a strong SPO: the long axis coincides with [100] and aligns with the shear direction, while the short axis forms a girdle between [100] and [010]. This correlation indicates that orthopyroxene CPO is governed by its SPO.</div><div>We propose that once orthopyroxene crystallizes, the longest facet developing along [001] followed by crystal rotation into the shear direction. Our experiments replicate natural microstructures and CPO observed in melt–rock reacted peridotites, supporting a model where orthopyroxene CPO forms through SPO-controlled rotation during crystallization. This mechanism provides a diagnostic tool to recognize synkinematic melt–rock reactions and to interpret fossil melt pathways in natural peridotites.</div></div>","PeriodicalId":22257,"journal":{"name":"Tectonophysics","volume":"918 ","pages":"Article 230974"},"PeriodicalIF":2.6,"publicationDate":"2025-10-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145383417","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}
Pub Date : 2025-10-29DOI: 10.1016/j.tecto.2025.230972
Zheng Xu , Yong Li , Guixi Yi , Liyuan Peng , Xin Yang , Wanzhang Wen , Shaoze Zhao
To investigate and analyze the impact of stress transfer and concentration driven by the 2008 Wenchuan Ms 8.0 earthquake on the Longmenshan-foreland basin, this study aims to predict the regions where future triggered earthquakes may occur and assess their seismic hazard levels.This paper utilizes finite element numerical simulations to assess the changes in regional stress fields after the Wenchuan earthquake, analyzes the entire process of stress transfer and redistribution under strong earthquake conditions, and fits the results with subsequent seismic events. The results are further validated by the stress fields revealed through the extensive aftershock source mechanism solutions in the study area, exploring the trends for future earthquake triggering. Results indicate: (1) During the earthquake, the stress concentration characteristics of the Beichuan-Yingxiu Fault is prominent, with the maximum principal stress ranging from (1.05–1.75) MPa. The cumulative strain energy in the segment north of Yingxiu along the Longmen Shan Fault is approximately 4–5 times that of the segment south of Yingxiu, which is speculated to be one of the important reasons for the frequent aftershocks in the northern segment of the Longmen Shan Fault. (2) After the earthquake, significant strain enhancement is observed in the southern segment of the Longmen Shan Fault and the Longquanshan Fault, with strain values ranging from (2.00–2.50) × 10−2. This is inferred to be the cause of the triggering earthquakes that occurred sequentially in the southern segment of the Longmen Shan Fault and the Chengdu Basin after the Wenchuan earthquake. (3) Based on the simulation results and stress field data, we identify 4 seismic hazard zones in the study area. Notably, the fault segments in the Longmen Shan foothills, specifically the Dayi-Dujiangyan section and the southern segment of the Lushan-Yingxiu section (the Dayi seismic gap), exhibit high levels of seismic hazard.
{"title":"Numerical simulation of stress transfer and triggered earthquake prediction along the Longmenshan-Foreland Basin driven by the Wenchuan Ms 8.0 earthquake","authors":"Zheng Xu , Yong Li , Guixi Yi , Liyuan Peng , Xin Yang , Wanzhang Wen , Shaoze Zhao","doi":"10.1016/j.tecto.2025.230972","DOIUrl":"10.1016/j.tecto.2025.230972","url":null,"abstract":"<div><div>To investigate and analyze the impact of stress transfer and concentration driven by the 2008 Wenchuan <em>M</em>s 8.0 earthquake on the Longmenshan-foreland basin, this study aims to predict the regions where future triggered earthquakes may occur and assess their seismic hazard levels.This paper utilizes finite element numerical simulations to assess the changes in regional stress fields after the Wenchuan earthquake, analyzes the entire process of stress transfer and redistribution under strong earthquake conditions, and fits the results with subsequent seismic events. The results are further validated by the stress fields revealed through the extensive aftershock source mechanism solutions in the study area, exploring the trends for future earthquake triggering. Results indicate: (1) During the earthquake, the stress concentration characteristics of the Beichuan-Yingxiu Fault is prominent, with the maximum principal stress ranging from (1.05–1.75) MPa. The cumulative strain energy in the segment north of Yingxiu along the Longmen Shan Fault is approximately 4–5 times that of the segment south of Yingxiu, which is speculated to be one of the important reasons for the frequent aftershocks in the northern segment of the Longmen Shan Fault. (2) After the earthquake, significant strain enhancement is observed in the southern segment of the Longmen Shan Fault and the Longquanshan Fault, with strain values ranging from (2.00–2.50) × 10<sup>−2</sup>. This is inferred to be the cause of the triggering earthquakes that occurred sequentially in the southern segment of the Longmen Shan Fault and the Chengdu Basin after the Wenchuan earthquake. (3) Based on the simulation results and stress field data, we identify 4 seismic hazard zones in the study area. Notably, the fault segments in the Longmen Shan foothills, specifically the Dayi-Dujiangyan section and the southern segment of the Lushan-Yingxiu section (the Dayi seismic gap), exhibit high levels of seismic hazard.</div></div>","PeriodicalId":22257,"journal":{"name":"Tectonophysics","volume":"918 ","pages":"Article 230972"},"PeriodicalIF":2.6,"publicationDate":"2025-10-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145383420","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}
Peloponnese is a seismotectonically active region in Greece (Eastern Mediterranean) located just north of the Hellenic Subduction Zone, along which the Aegean and Nubian continental plates converge, and south of the Corinth Gulf, a rapidly extending rift. In addition to these highly tectonically active margins, the crust of the Peloponnese is undergoing deformation, which has locally generated significant earthquakes. In this paper, an upper crustal deformation analysis has been performed in order to comprehend i) how much and under which mechanism this region is deforming, ii) whether our results can explain the past seismicity, and iii) whether areas of low recorded seismic activity till recently are prone to a possible future increase of activity, a vital piece of information in terms of seismic hazard assessment. This analysis was based on primary geodetic raw data, collected by 32 permanent GPS/GNSS stations, which monitor the wider Peloponnese region. Considering these measurements, the geodetic strain parameters were estimated by implementing triangulation and interpolation methodologies, providing the qualitative and quantitative deformation properties of Peloponnese. The results show a wide-spread low deformation, mostly shear, with local highs in areas where seismic activity is evident; the 2008 Andravida earthquake is a typical example, as it is related to a right-lateral blind strike-slip fault. However, normal faulting with a dip-slip component also contributes to upper-crustal deformation in the study area, as demonstrated by seismic events such as the Sparta and Kalamata earthquakes. These results suggest that several seismically ‘quiet’ regions of Peloponnese (such as the eastern-northeastern part) show significant deformation, since the accumulated strain in these regions appears not to be released by smaller frequent events; therefore, they might have the potential of hosting moderate to strong earthquakes along localized zones of deformation in the future, indicated as areas with recorded higher strains.
{"title":"Seismotectonic implications for the Peloponnese (SW Greece) region based on geodetic crustal deformation analysis","authors":"Ilias Lazos , Sotirios Sboras , Sotirios Kokkalas , Vassilios Karastathis , Georgios Xiroudakis , Kyriaki Iordanidou , Dimitrios Galanakis , Christos Pikridas , Spyridon Bellas , Ioannis Karamitros , Evaggelos Mouzakiotis , Christos Kanellopoulos , Stylianos Bitharis , Alexandros Chatzipetros , Spyros Pavlides","doi":"10.1016/j.tecto.2025.230969","DOIUrl":"10.1016/j.tecto.2025.230969","url":null,"abstract":"<div><div>Peloponnese is a seismotectonically active region in Greece (Eastern Mediterranean) located just north of the Hellenic Subduction Zone, along which the Aegean and Nubian continental plates converge, and south of the Corinth Gulf, a rapidly extending rift. In addition to these highly tectonically active margins, the crust of the Peloponnese is undergoing deformation, which has locally generated significant earthquakes. In this paper, an upper crustal deformation analysis has been performed in order to comprehend i) how much and under which mechanism this region is deforming, ii) whether our results can explain the past seismicity, and iii) whether areas of low recorded seismic activity till recently are prone to a possible future increase of activity, a vital piece of information in terms of seismic hazard assessment. This analysis was based on primary geodetic raw data, collected by 32 permanent GPS/GNSS stations, which monitor the wider Peloponnese region. Considering these measurements, the geodetic strain parameters were estimated by implementing triangulation and interpolation methodologies, providing the qualitative and quantitative deformation properties of Peloponnese. The results show a wide-spread low deformation, mostly shear, with local highs in areas where seismic activity is evident; the 2008 Andravida earthquake is a typical example, as it is related to a right-lateral blind strike-slip fault. However, normal faulting with a dip-slip component also contributes to upper-crustal deformation in the study area, as demonstrated by seismic events such as the Sparta and Kalamata earthquakes. These results suggest that several seismically ‘quiet’ regions of Peloponnese (such as the eastern-northeastern part) show significant deformation, since the accumulated strain in these regions appears not to be released by smaller frequent events; therefore, they might have the potential of hosting moderate to strong earthquakes along localized zones of deformation in the future, indicated as areas with recorded higher strains.</div></div>","PeriodicalId":22257,"journal":{"name":"Tectonophysics","volume":"918 ","pages":"Article 230969"},"PeriodicalIF":2.6,"publicationDate":"2025-10-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145383875","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}
This study investigates the conditions sustaining long-lived molten plutons in the middle to upper crust, driven by lower crustal melting due to magmatic underplating and episodic melt extraction. Using 2D two-phase flow models solving conservation equations for mass, composition, momentum, and energy, and assuming a simplified melting law, we examine the interplay between long-term magmatic processes (e.g., lower crust heating, melt generation, segregation, diapiric ascent) and short-term dynamics (e.g., magma extraction, dyke ascent, emplacement). A novel melt extraction and intrusion formulation is introduced, varying parameters such as melt extraction volume threshold, intrusion depth, size, and geometry. Results indicate that smaller extraction thresholds lead to more frequent intrusions, increasing total melt volume in the intrusion and prolonging pluton lifespan. Intrusion geometry strongly influences melt accumulation: small radii (∼2 km) favor significant melt volumes, while larger zones (>4 km) promote rapid freezing. Circular intrusions retain heat longer than dyke- or sill-like intrusions. Frequent intrusions promote vertical stacking of melt batches, pluton floor subsidence, and compositional stratification. Model-derived magma supply rates (0.15–0.3 km3/yr per extraction pulse; 0.001–0.002 km3/yr averaged over the total time extraction events) align with observed Central Andean magmatic systems. Melt extraction accelerates heat transport, producing early heat flux peaks (0.5–2 Myr) via the heat pipe mechanism, introduced in geoscience literature as a rapid transport of heat and mass through the lithosphere. This effect, quantified by a Nusselt number, increases with greater extracted melt volumes and shallower intrusions. Comparison with Central Andean heat flux data suggests a heat pipe Nusselt number of ∼3.5, indicating extraction and intrusion enhance heat transport by this factor. These findings provide insights into the interplay between magmatism, heat transfer, and pluton evolution in continental crust.
{"title":"Magma transfer and pluton growth: Modelling short- and long-term processes by thermo-mechanical two-phase flow including the heat pipe mechanism","authors":"Harro Schmeling , Gabriele Marquart , Herbert Wallner , Roberto Weinberg","doi":"10.1016/j.tecto.2025.230968","DOIUrl":"10.1016/j.tecto.2025.230968","url":null,"abstract":"<div><div>This study investigates the conditions sustaining long-lived molten plutons in the middle to upper crust, driven by lower crustal melting due to magmatic underplating and episodic melt extraction. Using 2D two-phase flow models solving conservation equations for mass, composition, momentum, and energy, and assuming a simplified melting law, we examine the interplay between long-term magmatic processes (e.g., lower crust heating, melt generation, segregation, diapiric ascent) and short-term dynamics (e.g., magma extraction, dyke ascent, emplacement). A novel melt extraction and intrusion formulation is introduced, varying parameters such as melt extraction volume threshold, intrusion depth, size, and geometry. Results indicate that smaller extraction thresholds lead to more frequent intrusions, increasing total melt volume in the intrusion and prolonging pluton lifespan. Intrusion geometry strongly influences melt accumulation: small radii (∼2 km) favor significant melt volumes, while larger zones (>4 km) promote rapid freezing. Circular intrusions retain heat longer than dyke- or sill-like intrusions. Frequent intrusions promote vertical stacking of melt batches, pluton floor subsidence, and compositional stratification. Model-derived magma supply rates (0.15–0.3 km<sup>3</sup>/yr per extraction pulse; 0.001–0.002 km<sup>3</sup>/yr averaged over the total time extraction events) align with observed Central Andean magmatic systems. Melt extraction accelerates heat transport, producing early heat flux peaks (0.5–2 Myr) via the heat pipe mechanism, introduced in geoscience literature as a rapid transport of heat and mass through the lithosphere. This effect, quantified by a Nusselt number, increases with greater extracted melt volumes and shallower intrusions. Comparison with Central Andean heat flux data suggests a heat pipe Nusselt number of ∼3.5, indicating extraction and intrusion enhance heat transport by this factor. These findings provide insights into the interplay between magmatism, heat transfer, and pluton evolution in continental crust.</div></div>","PeriodicalId":22257,"journal":{"name":"Tectonophysics","volume":"918 ","pages":"Article 230968"},"PeriodicalIF":2.6,"publicationDate":"2025-10-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145383439","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}
扫码关注我们
求助内容：
应助结果提醒方式：
京公网安备 11010802042870号