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In this study, we used the Pn tomography method to obtain detailed velocity and anisotropy structures of the uppermost mantle beneath Sakhalin–Kuril–Kamchatka region for improving the understanding of plate subduction, arc–arc collision, and volcanism. We found low Pn velocities beneath volcanoes and areas characterized by pronounced tectonic activity and high Pn velocities with strong anisotropy in the subducting plate. Low Pn velocity anomalies beneath southern Sakhalin connected the low‐velocity anomalies in the mantle and crust, indicating the ascent of fluid or melt, and may provide a magmatic source for the rear‐arc Rishiri volcano. In the absence of plate subduction, low‐velocity anomalies and north–south Pn anisotropy manifested beneath northern Kamchatka, revealing the lateral propagation of mantle flow beneath this northern region. We suggest that the eastern boundary of the slab window at the Kamchatka–Aleutian junction is likely to be located near the Komandorsky Islands. The Northwest Pacific region is prone to recurrent earthquakes and volcanic activities, attributable to plate subduction and multiple plate interactions. This study, focuses on elucidating the uppermost mantle structure beneath the Sakhalin–Kuril–Kamchatka region using seismic tomography. Beneath the island chain featuring volcanoes and areas with a lot of tectonic activity, seismic waves travel slower. This phenomenon implies the possible presence of magma or hot materials beneath these regions. In southern Sakhalin, a linkage is established through low Pn velocities connecting areas of low seismic wave velocity in the deeper mantle and crust. This linkage suggests a conduit for fluids or molten materials, potentially feeding for the Rishiri volcano situated beyond the volcanic arc. Strong low velocities, coupled with north–south Pn fast directions are identified beneath northern Kamchatka, indicating the northward propagation of mantle flow. Our imaging analysis suggests that the eastern edge of the slab window (the region where the plate is absent) at the Kamchatka–Aleutian junction is likely proximate to the Komandorsky Islands. This study provides new seismological insights into the plate collision and subduction processes as well as the deep structures in the Sakhalin–Kuril–Kamchatka region. Low Pn velocities clarify the upward path of the mantle‐derived thermal material beneath Sakhalin and its influence on surface volcanismStrong low Pn velocities and N–S anisotropy beneath northern Kamchatka signify the lateral propagation of mantle flow directed northwardThe eastern boundary of the slab window at the Kamchatka–Aleutian junction may be located near the Komandorsky Islands Low Pn velocities clarify the upward path of the mantle‐derived thermal material beneath Sakhalin and its influence on surface volcanism Strong low Pn velocities and N–S anisotropy beneath northern Kamchatka signify the lateral propagation of mantle flow directed northward The eastern boundary of the slab window at the Kamchatka–Aleutian junction may be located near the Komandorsky Islands

The eastern Tibetan Plateau (TP) is crucial to the exploration of plateau outgrowth mechanisms. Teleseismic attenuation may provide constraints on anelasticity in the lithosphere‐asthenosphere system and may therefore improve the understanding of plateau outgrowth and material extrusion. This study use dense array data across the eastern TP to measure relative attenuation from teleseismic P‐wave phases. These observations are then used to invert a 2D relative attenuation map and a 3D Qp−1model. Weak attenuation is observed beneath the Sichuan Basin and most of the Dianzhong Block at depths of both 0–100 km and 100–200 km (Qp−1< 0.003). Strong attenuation is observed beneath the eastern TP and southwestern Dianzhong Block at depths of 0–100 km (Qp−1∼ 0.01–0.13), but underneath the eastern TP only at depths of 100–200 km (Qp−1∼ 0.013–0.015). These results suggest a cratonic lithosphere underneath the Dianzhong Block similar to that beneath the Sichuan Basin. We assume that this is the cooled lithosphere remnant of the Permian Emeishan plume. In contrast, strong attenuation beneath the eastern TP would indicate a thick lower crust and asthenosphere with intense heating. The boundary between strong and weak attenuation lies close to the Longmenshan‐Xiaojinhe faults. We infer that the materials extruded eastward from the eastern TP cross this boundary into the southwestern Dianzhong Block in the lower crust, but stop at this boundary in the asthenosphere. Seismic attenuation describes the energy consumption of seismic waves which reflects subsurface anelasticity and so can provide constraints on the ductile materials in the lower crust and the asthenosphere. Here we present a 2D relative attenuation map and a 3D upper mantle Qp−1model for the eastern Tibetan Plateau. We find weak attenuation at depths above 200 km beneath the Sichuan Basin and most of the Dianzhong Block. Strong attenuation is observed beneath the southwestern Dianzhong Block at crustal depths, and underneath the eastern Tibetan Plateau at both crustal and asthenospheric depths. Our results suggest that the lithosphere beneath the Dianzhong Block has similar cratonic features to that beneath the Sichuan Basin. A thick and hot lower crust and asthenosphere with strong heat activity beneath the eastern Tibetan Plateau are also indicated by our attenuation images. Strong and weak attenuation are bordered by the Longmengshan‐Xiaojinhe faults. We would infer that the ductile materials extruded from the Tibetan Plateau cross this boundary into the southwestern Dianzhong Block in the lower crust, but not in the asthenosphere. Weak attenuation observations beneath the Dianzhong Block suggest the lithosphere there has similar cratonic features to that beneath the Sichuan BasinA thick lower crust and asthenosphere with strong heat activity beneath the eastern Tibetan Plateau are inferred from strong‐attenuation observationsThe eastward extrusion of the Tibetan Plateau crosses the Xiaojinhe Fault into the southwestern Dianzhong Block in the lower crust, but not in the asthenosphere Weak attenuation observations beneath the Dianzhong Block suggest the lithosphere there has similar cratonic features to that beneath the Sichuan Basin A thick lower crust and asthenosphere with strong heat activity beneath the eastern Tibetan Plateau are inferred from strong‐attenuation observations The eastward extrusion of the Tibetan Plateau crosses the Xiaojinhe Fault into the southwestern Dianzhong Block in the lower crust, but not in the asthenosphere

In recent years, many small‐ to moderate‐size earthquakes occurred in central northern Oklahoma, likely associated with wastewater injection. The most recent one is the M5.8 Pawnee earthquake occurred on 3 September 2016. It is still not clear what controls the locations of these injection‐induced earthquakes. Here we conduct 2‐D Pgwave tomography with anisotropy to image seismogenic structures in this region, using more than 10 years of Pgarrivals recorded by 81 seismic stations. Our high‐resolution Pgwave tomography shows two high‐velocity zones with northwest fast direction alternated by low‐velocity zones with northeast fast direction. The two dominant anisotropy directions are consistent with conjugated microfractures from surface faults and two nodal planes from focal mechanisms of moderate‐size earthquakes. Most moderate‐size (M> 4) earthquakes occurred either close to the boundaries between high‐ and low‐seismic velocity zones or within the high‐velocity zones, suggesting that they are associated with geological boundaries of different basement rock properties or with strong material properties in the upper crust. We suggest that although these moderate‐size earthquakes were induced by fluid injection, their spatial locations were likely controlled by local geologic structures. We obtain a high‐resolution Pgwave velocity and anisotropy structure in central northern OklahomaModerate‐size earthquakes mostly occurred along the boundaries marked by seismic velocity and anisotropy and gravity anomaliesLocal geologic structures likely control the locations of moderate‐size injection‐induced earthquakes

We analyze the teleseismic waveform data recorded by 42 temporary stations from the Y2 and ANTILOPE‐1 arrays using the Pand Sreceiver function techniques to investigate the lithospheric structure beneath western Tibet. The Moho is reliably identified as a prominent feature at depths of 55–82 km in the stacked traces and in depth migrated images. It has a concave shape and reaches the deepest location at about 80 km north of the Indus‐Yarlung suture (IYS). An intracrustal discontinuity is observed at ~55 km depth below the southern Lhasa terrane, which could represent the upper border of the eclogitized underthrusting Indian lower crust. Underthrusting of the Indian crust has been widely observed beneath the Lhasa terrane and correlates well with the Bouguer gravity low, suggesting that the gravity anomalies in the Lhasa terrane are induced by topography of the Moho. At ~20 km depth, a midcrustal low‐velocity zone (LVZ) is observed beneath the Tethyan Himalaya and southern Lhasa terrane, suggesting a layer of partial melts that decouples the thrust/fold deformation of the upper crust from the shortening and underthrusting in the lower crust. The Spconversions at the lithosphere‐asthenosphere boundary (LAB) can be recognized at depths of 130–200 km, showing that the Indian lithospheric mantle is underthrusting with a ramp‐flat shape beneath southern Tibet and probably is detached from the lower crust immediately under the IYS. Our observations reconstruct the configuration of the underthrusting Indian lithosphere and indicate significant along strike variations. An intracrustal discontinuity is observed at ~55 km depth representing the upper border of the underthrusting Indian lower crustThe midcrustal low‐velocity zone at ~20 km depth is clearly visible, which reflects the presence of partially melt crustThe LAB images indicate that the Indian lithospheric mantle is underthrusting beneath the southern Tibet with ramp‐flat shape

Eastern Asia is a prime location for the study of intracontinental tectono‐magmatic activity. For instance, the origin of widespread intraplate volcanism has been one of the most debated aspects of East Asian geological activity. Measurements of attenuation of teleseismic phases may provide additional constraints on the source regions of volcanism by sampling the upper mantle. This study uses data from three seismic arrays to constrain lateral variations in teleseismic Pwave attenuation beneath the Central Asian Orogenic Belt and the North China Craton. We invert relative observations of attenuation for a 2‐D map of variations in attenuation along with data and model uncertainties by applying a Hierarchical Bayesian method. As expected, low attenuation is observed beneath the Ordos block. High attenuation is observed beneath most of the volcanoes (e.g., the Middle Gobi volcano, the Bus Obo volcano, and the Datong volcano) in the study area, and estimated asthenospheric Qp values span from 95 to 200. These values are within the range of globally average asthenosphere. We infer that these volcanoes may tap melt from ambient asthenosphere and occur where the lithosphere is thin, which is consistent with previous petrologic studies. More complex mantle drivers of volcanism are not rejected but are not needed to explain eruptions in this area. In contrast, at the Xilinhot‐Abaga volcanic site, the observed low attenuation (as low as beneath the Ordos block) excludes a typical shallow melting column. Fluids from the subducted Pacific plate may initiate the deep melting and would be consistent with petrological constraints. Seismic attenuation, the loss of energy in a seismic wave as it passes through a medium, provides complementary constraints on the Earth's interior to those provided by the more common studies of seismic velocity. We present the first map of the attenuation experienced by the first arriving Pphase from distant earthquakes in the Central Asian Orogenic Belt and North China Craton. The Pphase from distant earthquakes travels nearly vertically beneath the stations that record them, and so variations in their attenuation reflect variations in the attenuation below the stations. We find low attenuation beneath the Ordos Block and high attenuation beneath most of the volcanic sites in the study region (e.g., the Middle Gobi volcano, the Bus Obo volcano, and the Datong volcano), where our results suggest that the asthenosphere is as about as attenuating as normal asthenosphere across the globe. We infer most of the volcanism in this portion of Eastern Asia taps melt from the ambient asthenosphere where the lithosphere is thin. This hypothesis is consistent with previous petrologic studies and does not require invoking unusual conditions such as a mantle plume. Counterintuitively, low attenuation is observed beneath the Xilinhot‐Abaga volcanic site, which excludes a shallow melting column beneath most volcanoes and requires a deep source. Taken together, our results support the hypothesis that lithospheric thickness is a primary driver of variations in the composition of erupted lavas. The teleseismic Pwave attenuation is obtained in the Central Asian Orogenic Belt and North China CratonMost volcanism in study area may tap melt from ambient asthenosphere and occur where the lithosphere is thinA thick lithosphere and a deep magma source are inferred beneath the Xilinhot‐Abaga volcanic site The teleseismic Pwave attenuation is obtained in the Central Asian Orogenic Belt and North China Craton Most volcanism in study area may tap melt from ambient asthenosphere and occur where the lithosphere is thin A thick lithosphere and a deep magma source are inferred beneath the Xilinhot‐Abaga volcanic site

We employ the P and S receiver function technique to data from the 44 seismic stations deployed in the eastern Himalayan syntaxis to investigate the crustal thickness, the average Poisson's ratio, and the depth of the lithosphere-asthenosphere boundary (LAB). The observed crustal thickness exhibits an overall NE-deepening trend, varying from 55 to 75 km. Two anomalous areas lie in the west and east of the Namche Barwa syntaxis characterized by thinner and thicker crust, respectively. The average Poisson's ratios within the study area are low in the north and moderate elsewhere with some high values in the south, consistent with felsic and intermediate rocks forming the crust. Our migrated images reveal that (1) the LAB of the Tibetan plate exists at relatively shallow depths (~110 km) and exhibits a gap beneath the Namche Barwa syntaxis, which may have formed by the delamination of mantle lithosphere due to local mantle upwelling, and (2) the LAB of the Asian plate is observed at a depth of ~180 km, which implies that the Asian plate has advanced southward to about 30°N under the Lhasa terrane. Our results provide new insights into the understanding of continental subduction and lithospheric deformation of the eastern Himalayan syntaxis. We image the lithospheric structure of eastern Himalayan synstaxisThe Tibetan plate exhibits a gap beneath Namche Barwa syntaxisThe Asian plate has advanced southward to about 30°N

To explore the west‐east variations in the underthrusting Indian lithosphere, we investigate the lithospheric structure using P and S receiver functions obtained from a west‐east linear array of 19 broadband stations spanning the Tethyan Himalaya at 85.5–88.5°E. Our observations of the Main Himalayan Thrust (MHT) and Moho serving as the top and bottom boundaries at depths of 42–54 km and 60–72 km, respectively, suggest that a thinning Indian lower crust with an eastward inclined geometry is underthrusting beneath the Tethyan Himalaya. An intra‐crustal low velocity zone (LVZ) immediately above the MTH at depths of 32–42 km is imaged, likely resulting from the presence of crustal dehydration partial melting. We propose that this LVZ induces the southward extrusion of melt‐weakened crustal material with itself as a channel and facilitates the development of duplexing structures, by which Indian lower crustal materials could be accreted into the Himalayan wedge along the north‐south mid‐crustal ramp in the MHT. The eastward dipping lithosphere‐asthenosphere boundary is clearly observed ranging from 90 to 126 km, which generally coincides with the changing trends of the MHT and Moho. These observations can be attributed to the eastward steepening subduction angle of the Indian lithosphere. We investigate the west‐east lithospheric structure beneath the Tethyan Himalaya using P and S receiver functionsThe Main Himalayan Thrust, Moho and a low velocity zone characterized by the pronounced eastward inclined trends are clearly imagedThe eastward dipping shape of the underthrusting Indian lithosphere is likely caused by the eastward steepening subduction angle We investigate the west‐east lithospheric structure beneath the Tethyan Himalaya using P and S receiver functions The Main Himalayan Thrust, Moho and a low velocity zone characterized by the pronounced eastward inclined trends are clearly imaged The eastward dipping shape of the underthrusting Indian lithosphere is likely caused by the eastward steepening subduction angle