Heilongjiang Earthquake Agency

Hydraulic fracturing is a key technology in shale gas extraction, whether hydraulic fracturing induces earthquakes has become a hot topic in the public and the focus of scholars’ research. The urgency of shale gas mining and the catastrophic nature of earthquakes highlight the urgent need to study this issue. The Changning anticline at the southern margin of the Sichuan Basin is a key area for shale gas exploitation. Taking this as an example, this paper applies the velocity model of the study area to reposition the M5.7 magnitude earthquake on December 16, 2018 and the M5.3 magnitude earthquake on January 03, 2019 and their aftershock sequence in this area. Using shale gas exploration drilling and reflection seismic data to carry out structural analysis, and recovering the tectonic geological setting of earthquake occurrence by restoring the formation process of the Changning anticline, to further explore the seismic mechanism. Our results show that the Changning anticline is a large basement fault-bend fold, and the displacement of the fault forming the anticline is 18 km, and the Changning anticline absorbs 33% of the fault slip. The Silurian Longmaxi Formation of the Changning anticline experienced larger-parallel shearing along underlying basement faults, forming a micro-fracture system. The footwall ramp of the basement fault is reactivated at present, earthquakes in this area mostly occur along the footwall ramp of the basement fault and above and below it. The anticlinal and synclinal hinge zones are also the earthquake concentration areas, but the earthquake magnitude decreases upwards along the kink-band, and small earthquakes below M2.0 occur in the Silurian Longmaxi Formation. So far, the earthquake in the Changning anticline mainly occurred in the southern limb of the anticline, which is a natural earthquake formed along the footwall ramp of the basement fault. The earthquakes in the Changning area are possible related to the geo-tectonic setting for the southeast outward compression of the Qinghai-Tibet Plateau at present, the moderate or large-scale earthquakes in the southwest Sichuan Basin are mainly due to the reactivation during late Quaternary of the earlier formed faults. It is suggested to carry out scientific monitoring of seismic activities in shale gas development zones.

Abstract The release of radon in active fault zones is a sustained radioactive pollution source of the atmospheric environment. The species, concentration and flux of radon emitted in soil gas in active fault zones in the Capital of China were investigated by in-situ field measurements. Two main species of radon discharging from soil gas in active fault zones were identified, including radon diffused and dispersed from permeable soil, and upwelling from faults. Higher concentrations and flux of radon from faults were observed in the Bohai Bay Basin due to the accumulated uranium in the sandstone reservoirs and higher permeability of the strata and bed rocks. Increased radon released by strong earthquakes persists, with the max flux of 334.56 mBq m −2 s −1 observed in FN (Fengnan district) located at the epicenter of the 28 July, 1976 Tangshan M S 7.8 earthquake. The level of radon released in 8 of 22 locations within the Basin and Range Province (to the west of Taihangshan piedmont fault Zone) reached level 2, and 13 of 14 locations within the Bohai Bay Basin reached levels 2–4, according to the Chinese Code (GB 50325–2001, 2006). Corresponding protective and safety measures should be in place to protect the health of nearby residents, due to their exposure to radon emitted from the faults. Also, the concentration of radon in active fault zones should be investigated to assess the possible risk, before land-use is planned.

Clinical manifestations and epidemiological characteristics of Lyme disease in Hailin county, Heilongjiang Province, China have been reported. The clinical picture of erythema chronicum migrans (ECM) is variable. ECM in the form of annular erythematous patch is uncommon. It is an extensive and indurated lesion. In some instances, a vesicle or necrosis appears in the center of the lesion. Secondary erythema may present in some patients. The neurologic abnormalities consist of meningitis, facial palsy, and polyneuritis. Cardiac abnormalities are rare. In addition, there were cases with lymphadenosis benigna cutis (LABC), which had heretofore only been reported in Europe. The attack rate of ECM is 8.4%. There was a significant sex difference, and most cases occurred in May and June. All patients had a history of tick bite. The prevalence rates of neurologic abnormalities and arthritis were 4.6% and 6.6%, respectively. Three strains of spirochete that are closely related to Borrelia burgdorferi were isolated from Ixodes persulcatus ticks and facial palsy patients. From the above results it is concluded that a focus of Lyme disease exists in this region.

Abstract The Wudalianchi Volcano Field (WDF) is a typical intraplate volcano in northeast China with generation mechanism not yet well understood. As its last eruption was around 300 years ago, the present risk for volcano eruption is of particular public interest. We have carried out a high‐resolution ambient noise tomography to investigate the location of magma chambers beneath the volcanic cones with a dense seismic array of 43 seismometers and ~ 6 km spatial interval. Significant low‐velocity anomalies up to 10% are found at 7–13 km depth under the Weishan volcano, consistent with the pronounced high electrical‐conductivity anomalies from previous magnetotelluric survey. We propose these extremely low velocity anomalies can be interpreted as partial melting in a shallow magma chamber with volume at least 200 km 3 which may be responsible for most of the recent volcanic eruptions in WDF. Therefore, this magma chamber may pose a serious hazard for northeast China.

Abstract The Maidan fault, which is an east‐northeast trending fault in the southwestern Tian Shan, is a sinistral reverse fault that extends more than 400 km in length and constitutes the boundary between the southwestern Tian Shan and the Tarim Basin. Here we quantify its late Quaternary activity based on the interpretations of high‐resolution remote sensing images and detailed field investigations. In the Aheqi valley, an ~150‐km‐long active fault can be divided into northeastern and southwestern segments based on variations in its strike and geometry. Based on the analysis of its offset geomorphological features and the dating of Quaternary sediments, we estimate the late Quaternary shortening rate across the fault to be 1.19 ± 0.25 mm/year, the sinistral strike‐slip rate to be 1.56 ± 0.64 mm/year, and the oblique thrust rate to be 1.96 ± 0.69 mm/year. Active tectonics, GPS crustal deformation data, and seismic activity indicate that the deformation in the southwestern Tian Shan is characterized by out‐of‐sequence thrust faulting and folding. Late Quaternary deformation has been partitioned into low‐angle thrust faulting along the Kalpin Tagh foreland fold and thrust system and sinistral reverse faulting along the high‐angle range‐front Maidan fault. The sinistral Maidan fault acts as a nucleation point for slip partitioning system, which can be viewed as positive flower structure with its surrounding thrust faults.

The inhibitory regulators, known as immune checkpoints, prevent overreaction of the immune system, avoid normal tissue damage, and maintain immune homeostasis during the antimicrobial or antiviral immune response. Unfortunately, cancer cells can mimic the ligands of immune checkpoints to evade immune surveillance. Application of immune checkpoint blockade can help dampen the ligands expressed on cancer cells, reverse the exhaustion status of effector T cells, and reinvigorate the antitumor function. Here, we briefly introduce the structure, expression, signaling pathway, and targeted drugs of several inhibitory immune checkpoints (PD-1/PD-L1, CTLA-4, TIM-3, LAG-3, VISTA, and IDO1). And we summarize the application of immune checkpoint inhibitors in tumors, such as single agent and combination therapy and adverse reactions. At the same time, we further discussed the correlation between immune checkpoints and microorganisms and the role of immune checkpoints in microbial-infection diseases. This review focused on the current knowledge about the role of the immune checkpoints will help in applying immune checkpoints for clinical therapy of cancer and other diseases.

Abstract In order to have a better understanding of the lithosphere formation and modification of the Tien Shan orogenic belt, we construct a well‐defined shear wave velocity model of the crust and upper mantle with full‐wave ambient noise tomographic method. High‐quality empirical Green's functions at periods of 7–200 s are extracted from the cross correlation of the vertical component of continuous seismic data at 108 stations during 2012–2014. Our tomographic results show remarkable velocity variations between and within the major tectonic units from the crust down to the upper mantle. We observe very slow upper crust beneath the Tarim and Junggar sedimentary basins. The interior of the Tarim Basin shows strong seismic heterogeneities. The high‐velocity mantle lithosphere of the Tarim Basin underthrusts northward toward the central Tien Shan. Lithosphere underthrusting could trigger intrusion of hot mantle material and partial melting, in correspondence with the prominent low‐velocity anomalies observed in the lower crust and uppermost mantle of the central Tien Shan. In contrast, the connected high‐velocity upper mantle structure from Tarim Basin across eastern Tien Shan to Junggar Basin may reflect the convergent effect between the Tarim and Junggar Basins, which consequently prevents the asthenosphere upwelling. We observe low‐velocity anomalies in the upper mantle of the western Tien Shan, indicating continental crust of the Eurasia lithosphere that has been subducted toward the western Tien Shan. The observed structural variations along the Tien Shan orogenic belt suggest different tectonic mechanisms for the lithosphere formation and modification of the three segments along strike.

The spatiotemporal and especially the vertical distributions of dust aerosols play crucial roles in the climatic effect of dust aerosol. In the present study, the spatial-temporal distribution of dust aerosols over East Asia was investigated using Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observations (CALIPSO) retrievals (01/2007–12/2011) from the perspective of the frequency of dust occurrence (FDO), dust top layer height (TH) and profile of aerosol subtypes. The results showed that a typical dust belt was generated from the dust source regions (the Taklimakan and Gobi Deserts), in the latitude range of 25°N~45°N and reaching eastern China, Japan and Korea and, eventually, the Pacific Ocean. High dust frequencies were found over the dust source regions, with a seasonal sequence from high to low as follows: spring, summer, autumn and winter. Vertically, FDOs peaked at about 2 km over the dust source regions. In contrast, FDOs decreased with altitude over the downwind regions. On the dust belt from dust source regions to downwind regions, the dust top height (TH) was getting higher and higher. The dust TH varied in the range of 1.9–3.1 km above surface elevation (a.s.e.), with high values over the dust source regions and low values in the downwind areas, and a seasonally descending sequence of summer, spring, autumn and winter in accord with the seasonal variation of the boundary layer height. The annual AOD (Aerosol Optical Depth) was generally characterized by two high and two low AOD centers over East Asia. The percent contribution of the Dust Aerosol Optical Depth to the total AOD showed a seasonal variation from high to low as follows: spring, winter, autumn and summer. The vertical profile of the extinction coefficient revealed the predominance of pure dust particles in the dust source regions and a mixture of dust particles and pollutants in the downwind regions. The dust extinction coefficients over the Taklimakan Desert had a seasonal pattern from high to low as follows: spring, winter, summer and autumn. The results of the present study offered an understanding of the horizontal and vertical structures of dust aerosols over East Asia and can be used to evaluate the performance aerosol transport models.

Abstract The increased seismic activity of the last ~10 years in Changning county of Sichuan Province comprised just small (mostly M L < 5.0) injection‐induced earthquakes. The M W 5.7 earthquake on June 17, 2019, is the largest event ever reported there. Moment tensor of the mainshock was remarkably dominated by a compensated linear vector dipole. We resolve its fine structure showing it was a doublet, allowing approximation by a thrust‐ and strike‐slip subevent. The mainshock nucleated as thrust faulting, which (together with the largest aftershocks) can be linked with previously known reverse faults, favorably oriented to regional stress field. Contrarily, the strike‐slip segment of the mainshock, less favorably oriented, was probably facilitated by elevated pore pressure due to previous injections. Shallow active strike‐slip faulting, not yet mapped in the region, is a new feature, important for future hazard assessment.

Abstract. Size-resolved aerosol chemical compositions were measured continuously for 1.5 years from June 2010 to January 2012 with an aerosol mass spectrometer (AMS) to characterize the mass and size distributions (MSDs) of major chemical components in submicron particles (approximately PM1) at Mountain Tai (Mt. Tai), an elevated site in central east China. The annual mean mass concentrations of organic, sulfate, nitrate, ammonium, and chloride were 11.2, 9.2, 7.2, 5.8, and 0.95 μg m−3, respectively, which are much higher than those at most mountain sites in the USA and Europe, but lower than those at the nearby surface rural sites in China. A clear seasonality was observed for all major components throughout the study, with low concentration in fall and high in summer, and is believed to be caused by seasonal variations in planetary boundary layer (PBL) height, near surface pollutant concentrations and regional transport processes. Air masses were classified into categories impacted by PBL, lower free troposphere (LFT), new particle formation (NPF), in-cloud processes, and polluted aerosols. Organics dominated the PM1 mass during the NPF episodes, while sulfate contributed most to PM1 in cloud events. The average MSDs of particles between 30 and 1000 nm during the entire study for organics, sulfate, nitrate, and ammonium were approximately log-normal with mass median diameters (MMDs) of 539, 585, 542, and 545 nm, respectively. These values are slightly larger than those observed at ground sites within the North China Plain (NCP), likely due to the relative aged and well-mixed aerosol masses at Mt. Tai. There were no obvious differences in MMDs during the PBL, LFT, in-cloud and polluted episodes, but smaller MMDs, especially for organics, were observed during the NPF events. During the PBL, NPF, and polluted episodes, organics accounted for major proportions at smaller modes, and reached 70% at 100–200 nm particles in the polluted events. In cloud episodes, inorganics contributed 70% to the whole size range dominated by sulfate, which contributed 40% to small particles (100–200 nm), while organics occupied 20%, indicating that sulfate is a critical chemical component in cloud formation. Seven clusters of air masses were classified based on 72 h back-trajectory analysis. The majority of the regionally dispersed aerosols were found to be contributed from short distance mixed aerosols, mostly originated from the south with organics and sulfate as major components. Air masses from long range transport always brought clean and dry aerosols which resulted in low concentrations at Mt. Tai. AMS-PMF (positive matrix factorization) was employed to resolve the subtype of organics. Oxygenic organics aerosols (OAs) occupied 49, 56, 51, and 41% of OAs in the four seasons respectively, demonstrating that most OA were oxidized in summer due to strong photochemical reactions. Biomass burning OAs (BBOAs) accounted for 34% of OA in summer, mainly from field burning of agriculture residues, and coal combustion OAs (CCOAs) accounted for 22% of OA in winter from heating.

Abstract The Lenglongling fault (LLLF) is located along the northeastern margin of the Tibetan Plateau and forms a part of the Tianzhu seismic gap along the Qilian‐Haiyuan fault zone. Little is known about the recurrence of large earthquakes along the LLLF nor the associated seismic hazards of the gap. Here the six most recent surface rupturing paleoearthquakes of the LLLF are revealed by measurement of offset landforms, trench excavations, and radiocarbon dating. They are labeled E1–E6 from youngest to oldest, and their timings are constrained to the following time ranges: 636–498 to present, 2951–1155, 4016–3609, 5325–4476, 7284–6690, and 8483–7989 years BP, respectively. The LLLF displays evidence of fresh, recent surface rupture, and the trench sections reveal that the fault ruptured to the ground surface during the most recent event. Based on this fresh surface rupture and historical earthquake records, the latest event E1 was most likely the 1927 M 8.0 Gulang earthquake. In conjunction with previous studies, Gulang earthquake might be a complicated event characterized by the combined rupture of both strike‐slip and thrust faults. The average recurrence interval of the six paleoearthquakes is 1643 ± 568 years, and the coefficient of variation is 0.34, indicating that the LLLF follows a quasiperiodic recurrence model. Based on this new understanding of the last event, the LLLF may not be a part of the Tianzhu seismic gap. However, an earthquake of up to M W 7.6 could still rupture the gap sections composed of the Jinqianghe, Maomaoshan, and Laohushan faults.

The 2022 MS 6.8 Luding earthquake is the strongest earthquake in Sichuan Province, Western China, since the 2017 MS 7.0 Jiuzhaigou earthquake. It occurred on the Moxi fault in the southeastern segment of the Xianshuihe fault, a tectonically active and mountainous region with severe secondary earthquake disasters. To better understand the seismogenic mechanism and provide scientific support for future hazard mitigation, we summarize the preliminary results of the Luding earthquake, including seismotectonic background, seismicity and mainshock source characteristics and aftershock properties, and direct and secondary damage associated with the mainshock. The peak ground displacements in the NS and EW directions observed by the nearest GNSS station SCCM are ∼35 mm and ∼55 mm, respectively, resulting in the maximum coseismic dislocation of 20 mm along the NWW direction, which is consistent with the sinistral slip on the Xianshuihe fault. Back-projection of teleseismic P waves suggest that the mainshock rupture propagated toward south-southeast. The seismic intensity of the mainshock estimated from the back-projection results indicates a Mercalli scale of VIII or above near the ruptured area, consistent with the results from instrumental measurements and field surveys. Numerous aftershocks were reported, with the largest being MS 4.5. Aftershock locations (up to September 18, 2022) exhibit 3 clusters spanning an area of 100 km long and 30 km wide. The magnitude and rate of aftershocks decreased as expected, and the depths became shallower with time. The mainshock and two aftershocks show left-lateral strike-slip focal mechanisms. For the aftershock sequence, the b-value from the Gutenberg-Richter frequency-magnitude relationship, h-value, and p-value for Omori’s law for aftershock decay are 0.81, 1.4, and 1.21, respectively, indicating that this is a typical mainshock-aftershock sequence. The low b-value implies high background stress in the hypocenter region. Analysis from remote sensing satellite images and UAV data shows that the distribution of earthquake-triggered landslides was consistent with the aftershock area. Numerous small-size landslides with limited volumes were revealed, which damaged or buried the roads and severely hindered the rescue process.

Abstract The rupture patterns of large earthquakes in transpressional systems can provide important information for understanding oblique motion and strain partitioning between tectonic blocks. The 1927 M 8.0 Gulang earthquake occurred on the transpressional boundary between the Tibetan and Gobi‐Alashan blocks. Our results, combined with those of previous studies show that the Lenglongling fault (LLLF) and Southern Wuwei Basin fault (SWBF) have both ruptured during the Gulang earthquake, but they exhibited different motions. An ~120‐km‐long surface rupture zone formed along the LLLF, with a left‐lateral strike‐slip motion and a coseismic horizontal offset of ~2.4–7.5 m. Bending, bifurcation, and change of the slip sense occurs at both ends of the fault. An ~42‐km‐long rupture zone formed along the SWBF, with a coseismic vertical offset of ~0.6–2.8 m. Thus, the Gulang earthquake is a complex rupture event where strike‐slip and thrust faults ruptured simultaneously. Analysis of deep and shallow structures and three‐dimensional finite‐element modeling reveal that the north dipping LLLF and the SWBF may converge downward to a low‐angle décollement, accommodating the strike‐slip and thrust motions during the earthquake, respectively. This pattern of deformation partitioning is similar to some other earthquakes where oblique block convergence is generally partitioned into strike‐slip motion on steeply dipping faults and vertical motion on gently dipping faults. Our study also suggests that the strain partitioning pattern in the NE Tibetan Plateau may be controlled by changes of the regional principal compressive stress directions and fault geometry at depth.

To better understand the cloud condensation nuclei (CCN) activation capacity of aerosol particles in different pollution conditions, a long-term field experiment was carried out at a regional GAW (Global Atmosphere Watch) station in the Yangtze River Delta area of China. The homogeneity of aerosol particles was the highest in clean weather, with the highest active fraction of all the weather types. For pollution with the same visibility, the residual aerosol particles in higher relative humidity weather conditions were more externally mixed and heterogeneous, with a lower hygroscopic capacity. The hygroscopic capacity (κ) of organic aerosols can be classified into 0.1 and 0.2 in different weather types. The particles at ~150 nm were easily activated in haze weather conditions. For CCN predictions, the bulk chemical composition method was closer to observations at low supersaturations (≤0.1%), whereas when the supersaturation was ≥0.2%, the size-resolved chemical composition method was more accurate. As for the mixing state of the aerosol particles, in haze, heavy haze, and severe haze weather conditions CCN predictions based on the internal mixing assumption were robust, whereas for other weather conditions, predictions based on the external mixing assumption were more accurate.

As the fourth pole of China's economic growth, the Chengdu-Chongqing urban agglomeration plays a significant role in reinforcing the ecological barrier in the upper reaches of the Yangtze River, and is crucial for ecological and environmental protection strategies. In this paper, Google Earth Engine (GEE) and the MODIS images from 2000, 2005, 2010, 2015, and 2022 were utilized to construct the Improved Remote Sensing Ecological Index (IRSEI) to characterize the ecological quality more accurately than RSEI. Additionally, combined with nighttime light remote sensing data, land use data and socio-economic data, the GDP sub-industry spatialization model was utilized to analyze the urbanization process in depth. To dynamically monitor and evaluate the interaction between urbanization and ecological environment quality, a coupling coordination model incorporating the above methods was developed. The results show that (1) The effective information of the IRSEI in ecological quality analysis increased by 3.26% compared to RSEI, and the correlation with each ecological index was higher; (2) The ecological environment quality of the Chengdu-Chongqing urban agglomeration peaked in 2005 and has been declining since then, with the rate of decline gradually slowing down from 2005 to 2022; (3) The GDP sub-industry spatialization model is more suitable for characterizing the scattered villages, and can effectively exhibit the urbanization process. From 2000 to 2022, urbanization was rapidly developed, and the level of core cities such as Chengdu and Chongqing far exceeded those of neighboring cities; (4) The coupling coordination level between IRSEI and GDP spatialization model generally increased, indicating ongoing improvements in the synergy between ecological environment and urbanization in the Chengdu-Chongqing urban agglomeration. This study developed a method for quickly monitoring and assessing the relationship between ecological environment quality and urbanization by using IRSEI and GDP sub-industry spatialization model, and provides scientific analytical methods and data support for monitoring and governing the ecological environment in emerging urban agglomerations.

Abstract Myanmar, one of the most active tectonic regions in the world, endures the risk of destructive earthquakes. Based on seismic data recorded at the recently deployed dense array of the China‐Myanmar Geophysical Survey in the Myanmar Orogen (CMGSMO), we detect 854 and locate 599 shallow earthquakes with high precision and determine the focal mechanisms of 40 earthquakes. We identify two NW‐SE trending fault zones accommodating dextral strike‐slip earthquakes beneath the Central Basin, indicating potential seismic risk in the region. We also recognize a nearly N‐S trending seismic zone in the overlying Indo‐Burma Ranges (IBR) crust near the Kabaw Fault (KBF). The earthquakes within this seismic zone mostly show thrusting focal mechanisms. Our results suggest that strike‐slip deformation dominates to the east of the KBF, while shortening is mainly confined to the west of the KBF in Central Myanmar.

Lushan Yunwu Tea is one of a unique Chinese tea series, and total polyphenols (TP), free amino acids (FAA), and polyphenols-to-amino acids ratio models (TP/FAA) represent its most important taste-related indicators. In this work, a feasibility study was proposed to simultaneously predict the authenticity identification and taste-related indicators of Lushan Yunwu tea, using near-infrared spectroscopy combined with multivariate analysis. Different waveband selections and spectral pre-processing methods were compared during the discriminant analysis (DA) and partial least squares (PLS) model-building process. The DA model achieved optimal performance in distinguishing Lushan Yunwu tea from other non-Lushan Yunwu teas, with a correct classification rate of up to 100%. The synergy interval partial least squares (siPLS) and backward interval partial least squares (biPLS) algorithms showed considerable advantages in improving the prediction performance of TP, FAA, and TP/FAA. The siPLS algorithms achieved the best prediction results for TP (RP = 0.9407, RPD = 3.00), FAA (RP = 0.9110, RPD = 2.21) and TP/FAA (RP = 0.9377, RPD = 2.90). These results indicated that NIR spectroscopy was a useful and low-cost tool by which to offer definitive quantitative and qualitative analysis for Lushan Yunwu tea.

We installed 10 continuous Global Positioning System (GPS) stations on the northeast margin of the Tibetan Plateau at the end of 2012, in order to qualitatively investigate strain accumulation across the Liupanshan Fault (LPSF). We integrated our newly built stations with 48 other existing GPS stations to provide new insights into three-dimensional tectonic deformation. We employed white plus flicker noise model as a statistical model to obtain realistic velocities and corresponding uncertainties in the ITRF2014 and Ordos-fixed reference frame. The total velocity decrease from northwest to southeast in the Longxi Block (LXB) was 5.3 mm/yr within the range of 200 km west of the LPSF on the horizontal component. The first-order characteristic of the vertical crustal deformation was uplift for the northeastern margin of the Tibetan Plateau. The uplift rates in the LXB and the Ordos Block (ORB) were 1.0 and 2.0 mm/yr, respectively. We adopted an improved spherical wavelet algorithm to invert for multiscale strain rates and rotation rates. Multiscale strain rates showed a complex crustal deformation pattern. A significant clockwise rotation of about 30 nradians/yr (10−9 radians/year) was identified around the Dingxi. Localized strain accumulation was determined around the intersectional region between the Haiyuan Fault (HYF) and the LPSF. The deformation pattern across the LFPS was similar to that of the Longmengshan Fault (LMSF) before the 2008 Wenchuan MS 8.0 earthquake. Furthermore, according to the distributed second invariant of strain rates at different spatial scale, strain partitioning has already spatially localized along the Xiaokou–Liupanshan–Longxian–Baoji fault belt (XLLBF). The tectonic deformation and localized strain buildup together with seismicity imply a high probability for a potential earthquake in this zone.

Abstract Seismology illuminates physical processes occurring during underground explosions, not all yet fully understood. The thus‐far strongest North Korean test of 3 September 2017 was followed by a moderate seismic event ( m L 4.1) after 8.5 min. Here we provide evidence that this aftershock was a nontectonic event which radiated seismic waves as a buried horizontal closing crack. This vigorous crack closure, occurring shortly after the blast, is studied in the North Korea test site for the first time. The event can be qualitatively explained as rapid destruction of an explosion‐generated cracked rock chimney due to cavity collapse, although other compaction processes cannot be ruled out.

Abstract Widespread rotations of maximum compressive stress in the upper crust are revealed in eastern Tibet by the focal mechanism stress inversion technique. Because of the good correlation with locations of folds, anticlines, and mountains in the region, the upper crustal stress variation is related to the lateral displacement of upper crust. To compare deformations in upper crust and upper mantle, we use SKS/SKKS splitting measurements to investigate the seismic anisotropy in eastern Tibet. The fast polarization directions subparallel to the strikes of faults in Chuandian fragment and southern boundary tectonic belt. This may indicate that the induced anisotropy mainly resulted from alignment of fault fabrics by strong shearing along strike‐slip faults, while the widespread stress rotations and systemic angular difference between upper crustal stress field and seismic anisotropy suggest that the decoupling of upper crustal deformation from middle‐lower crust by a series of detachments in the process of the crust thickening resulted from the obstruction of eastward expansion by Sichuan Basin.