Maduo County Research Articles

Enhancing Wetland Landscape Connectivity through Multi-Factor Optimization: a Case Study in Maduo County, Qinghai Province, China

Enhancing Wetland Landscape Connectivity through Multi-Factor Optimization: a Case Study in Maduo County, Qinghai Province, China

Machine-learning based location of the 2021 MW 7.4 Maduo, Qinghai, China earthquake sequence: Insight into intraplate seismogenesis

On 22 May 2021, an MW 7.4 earthquake occurred in Maduo County, Qinghai Province, China, which is located on the Kunlun Mountain Pass-Jiangcuo fault inside the Bayan Har block, providing a good opportunity to investigate seismogenesis of large intraplate earthquakes. We analyze two years of continuous seismic data from June 2021 to June 2023, which were recorded at 34 portable seismic stations of the MaduoArray deployed in the source zone by our group. The LOC-FLOW workflow of automatic detection and location is applied to construct a complete and high-precision seismic catalog for the region, which includes machine-learning phase picking (PhaseNet), earthquake phase association (REAL), velocity model updating and station correction (VELEST), absolute earthquake location (HypoInverse), and relative location (HypoDD). As a result, 78,832 Maduo aftershocks and other local earthquakes are detected and relocated precisely. Our results show that the length of the Maduo aftershock zone is ∼170 km, which is mainly distributed along the NWW-SEE oriented Kunlun Mountain Pass-Jiangcuo fault, and there is a horsetail bifurcation feature at the eastern end of the aftershock sequence. The seismogenic fault is nearly vertical, and local seismicity occurs on both sides of the fault. Our results also show that there is no seismic gap or aftershock sparse area in the region. Previous studies have revealed a low-velocity and high-conductivity anomaly below the source zone, reflecting fluids ascending from the lower crustal flow. These results provide new insights into the cause of the 2021 Maduo earthquake.

Relocation of the 2021 MW 7.4 Maduo, Qinghai, China earthquake sequence and implications for seismogenic structure

An MW 7.4 earthquake struck Maduo County, Qinghai, China on 22 May 2021. To better understand the seismogenic structure of this region, we collect local earthquake arrival time data at the MAD station in the China Earthquake Networks Center observational bulletins during 1 June to 20 September 2021, and manually pick P and S wave arrival times from high-quality seismograms recorded at 34 recently deployed MaduoArray portable seismic stations. Using these arrival times, we relocate the Maduo earthquake sequence using earthquake association, absolute location and relative location methods. Our results show that the 2021 Maduo earthquake sequence occurred along the Kunlun Mountain Pass-Jiangcuo fault zone in the NWW-SEE direction and the aftershocks are located on both sides of the mainshock, showing characteristics of bilateral rupture. Vertical cross-sections of the aftershock distribution illustrate a nearly vertical shape of the seismogenic fault that tilts toward the northeast and southwest in different sections, reflecting a complex geometry of the fault plane. There is a horsetail bifurcation phenomenon at the eastern end of the fault zone. A sparse area of aftershocks appears at about 30 km east of the mainshock epicenter, which may be associated with a uniform fault friction and sufficient release of rupture energy caused by super-shear rupture of the mainshock. Taking into account many geophysical results including seismic tomography and magnetotelluric soundings, we speculate that the occurrence of the Maduo earthquake could be affected by crustal fluids in the fault zone. The fluids may ascend from the lower crustal flow beneath northeastern Tibet.

Three-dimensional displacement and slip distribution of the 2021 Mw 7.4 Maduo (Tibetan Plateau) earthquake determined by GNSS and InSAR

On May 22, 2021, an Mw 7.4 earthquake occurred on the Maduo-Jiangcuo fault, located in Maduo County, Qinghai Province (China). According to the co-seismic deformation and the three-dimensional displacement reached from the interferometric synthetic aperture radar (InSAR) and the global navigation satellite system (GNSS), the rupture trace in the NWW direction was mapped, spanning a length of approximately 160 km and the earthquake happened on a typical sinistral strike-slip fault. In three-dimensional displacement, the displacement in E-W was bigger than that in N-S and vertical, with the RMSE 3.01 mm, 15.28 mm, and 5.16 mm respectively. Moreover, the slip distribution inverted with the homogeneous half-space model and layered half-space model, indicated that the corresponding magnitude was 7.3 Mw and 7.4 Mw, and the corresponding peak slip was 5.53 m and 5.96 m. The correlation coefficients of observed and predicted both exceeded 0.791, meeting the need for slip inversion. What is more, the peak inversion depth was no more than 15 km with strike angle and dip angle of 269° and 82.9° in the homogeneous half-space model and 265° and 83.7° in the layered half-space model, respectively. In addition, the Coulomb stress changes decreased on the Maduo-Jiangcuo fault and accumulated on the East Kunlun fault, which might cause aftershocks and future earthquakes were still possible. In short, the 2021 Mw7.4 Maduo earthquake made it possible to unravel seismic behavior in the Tibet plateau, which is of great significance for seismic hazard research.

Spatio-Temporal Characteristics and Driving Mechanism of Alpine Peatland InSAR Surface Deformation—A Case Study of Maduo County, China

Spatio-Temporal Characteristics and Driving Mechanism of Alpine Peatland InSAR Surface Deformation—A Case Study of Maduo County, China

Composite Source Model for Broadband Ground-Motion Simulations: 2021 Mw 7.4 Maduo, China, Earthquake Case Study

Abstract On 22 May 2021, at 2:40 a.m. (local time), an earthquake with a moment magnitude of 7.4 was reported to have occurred in Maduo County (34.59° N, 98.34° E), China. The focal depth was 17 km. After the earthquake, many scholars inverted the slip distribution of the Maduo earthquake based on ground-motion recordings, and the Global Positioning System and the Interferometric Synthetic Aperture Radar data. To verify the reliability of the fast estimation source model method adopted in this study, the hybrid slip model of the 2011 Mw 7.4 Maduo earthquake, in Qinghai Province, China, is synthetized based on the stochastic finite-fault model and the semiempirical relation between the earthquake magnitude (Mw) and source parameters. The truncated normal distribution and regional crustal structure are used to generate 30 sets of global source parameters, which describes that the deterministic characteristics of the source mainly include the size of the rupture fault, and the average slip, and the local source parameters. The local parameters include asperity and k2 model parameters. Finally, stochastic finite-fault modeling is adopted to synthetic the acceleration response spectra at four selected sites meeting different geological conditions and orientations, and the minimum residual principle is used to select the final slip model for the Maduo earthquake with the minimum residual of the average response spectra. The research results show that the width, maximum slip, and asperity body position of the source model estimated in this study are consistent with those of the inversion slip model, which verifies the reliability and applicability of this method. This work provides technical and theoretical support for rapid prediction of the source model of earthquakes with specific magnitudes.

Vegetation Types Variations to the South of Ngoring Lake from 2013 to 2020, Analyzed by Hyperspectral Imaging

Studying the variation in vegetation types within the source region of the Yellow River (SRYR) is of great significance for understanding the response of vegetation to climate change and human activities on the Qinghai-Tibet Plateau (QTP) permafrost. In order to understand the characteristics of the variation in vegetation associations in the SRYR under the influence of climate and human activities, two hyperspectral remote sensing images from HJ-1A in 2013 and OHS-3C in 2020 were used to extract the vegetation types located in the area south of Ngoring Lake, covering 437.11 km2 in Maduo County, from the perspective of vegetation associations. Here, the hybrid spectral CNN (HybridSN) model, which is dependent on both spatial and spectral information, was used for vegetation association classifications. On this basis, the variations in vegetation associations from 2013 to 2020 were studied using the transition matrix, and the variation in noxious weeds across different altitude and slope gradients was analyzed. As an example, Thermopsis lanceolata’s spatial distribution pattern and diffusion mechanism were analyzed. The results showed that (1) in addition to noxious weeds, herbage such as Poa poophagorum, Stipa purpurea, Kobresia humilis, and Carex moorcroftii increased, indicating that the overall ecological environment tended to improve, which may be attributed mainly to the development of a warm and humid climate. (2) Most of the noxious weeds were located at low altitudes with an area increase in the 4250–4400 m altitude range and a decrease in the 4400–4500 m altitude range. More attention should be given to the fact that the noxious weeds area increased from 2.88 km2 to 9.02 km2 between 2013 and 2020, which was much faster than that of herbage and may threaten local livestock development. (3) The Thermopsis lanceolate association characterized by an aggregated distribution tended to spread along roads, herdsmen sites, and degraded swamps, which were mainly affected by human activities and swamp degradation.

Analysis of seismic damage of a highway bridge during the 2021 Ms 7.4 earthquake in Maduo County, China

Analysis of seismic damage of a highway bridge during the 2021 Ms 7.4 earthquake in Maduo County, China

Three-dimensional coseismic displacements and slip distribution of the 2021 Mw 7.4 maduo earthquake: Synergy of SAR, InSAR and optical images

On 21 May 2021, an earthquake of moment magnitude (Mw) 7.4 occurred near Maduo county in Qinghai Province China. This is the first major earthquake that occurred in the interior of the Bayan Har block in the Tibetan Plateau over the past 70 decades. Focusing on this event, we conducted a study on three-dimensional (3D) coseismic displacement reconstruction and its tectonic implication. We acquired both Synthetic Aperture Radar (SAR) and optical imaging satellite imagery, including SAR images from Sentinel-1 and Advanced Land Observation Satellite-2 (ALOS-2) as well as the multi-spectrum images from the Sentinel-2 (S2) satellite. We applied the Interferometric SAR (InSAR) and pixel-offset tracking (POT) techniques to coseismic SAR data pairs and reconstructed two dimensional displacements. With the constructed displacement fields in multiple viewing directions, we resolved the 3D coseismic displacements (north-south, east-west, and up components) by integrating the regional strain model with variance components estimation (SM-VCE). We recommend using the standard deviation value at each grid cell, which can be calculated in the resampling, as the initial weight. Based on the resolved 3D coseismic displacements, we further estimated the dip angles for the two segments (F4 and F5) in the east of the rupture zone. The associated moment magnitude is about Mw7.4, which corresponds to the released energy of ∼ 1.74×1020 Nm.

A Topographic Perspective on the Propensity for Degradation of Plateau Swampy Meadows in Maduo County, West China

The swampy meadows atop the vast Qinghai–Tibet Plateau in West China fall into alpine, pediment, valley, floodplain, terrace, lacustrine, and riverine types according to their hydro-geomorphic properties. They have suffered degradation to various levels of severity due to climate change and external disturbance. In this paper, we studied the propensity of these types of swampy meadows to degrade from the topographic perspective. Evaluated against four degradation indicators of vegetation, hydrology, soil erosion, and pika (Ochotona curzoniae) damage, degradation severity at 106 swampy meadows representing all types of wetlands was graded to one of four levels, from which the field-based propensity to degrade (PtD) index value was derived. Judged against this index, terrace and alpine swampy meadows are the most prone to degradation while valley, lacustrine, and riverine swampy meadows are the least. The index value of a given swampy meadow type bears a close relationship (R2 = 0.916) with its rate of change during 1990–2013, which confirms the validity of the proposed index in predicting the propensity of swampy meadows to change. The observed differential PtD of different types of swampy meadows is attributed primarily to elevation (R2 = 0.746; p = 0.027) and, secondarily, to surface morphology (R2 = 0.696; p = 0.039). Thus, the elevation at which a swampy meadow is situated is a more important factor to its PtD than its surface morphology. In particular, swampy meadows located at a higher elevation with a convex surface are much more prone to degradation than those at a lower elevation of a concave slope. Such findings can guide the proper management of different types of swampy meadows to achieve sustainable animal husbandry.

Earthquake-induced risk assessment of cultural heritage based on InSAR and seismic intensity: A case study of Zhalang temple affected by the 2021 Mw 7.4 Maduo (China) earthquake

Earthquakes have been acknowledged as threats to heritages for a long time in the past decades. Many scientific publications and international guidelines have addressed this issue. However, the related reports are still lacking particularly for the 2021 Mw 7.4 Maduo earthquake and its surrounding heritage sites, even though this event was the largest earthquake in China after 2008 with 13 National Key Protected Cultural Relic Units (NKPCRUs) of China located in the surrounding areas within 200 km from the epicenter. On May 21, 2021, an Mw 7.4 earthquake struck Maduo County in Qinghai Province, China. The earthquake was large in magnitude and caused ∼150 km of surface rupture. The integrity and authenticity of cultural heritages near the epicenter are under severe threat, making it critically important to quantify the potential damages and vulnerability of these sites affected by the Mw 7.4 earthquake. Nevertheless, many geological and geophysical studies related to this earthquake have been conducted, but none of them consider the seismic damage to the heritage sites. To fulfill this gap, the Zhalang temple (also known as “Golok Peaceful Liberation Memorial”) which was a Tibetan Buddhist monastery located ∼140 km away from the Mw 7.4 epicenter of the 2021 Maduo earthquake was taken as an example to investigate whether and how the strong earthquake could affect a cultural heritage in such a distance. Collaborative monitoring based on InSAR and seismic intensity was conducted to measure the earthquake-induced deformation and characterize the risks and damages to cultural heritages by earthquakes. First, fast responses within 30 min based on the seismic method were performed. The PGV-vS30 intensity, that was the peak ground velocities (PGV) further site-corrected by the site conditions of the time-averaged shear-wave velocity to 30 m depth (vS30) seismic intensity map was obtained, which provided a general and fast guidance to preliminary determinations of the severe disaster area and the scope of the disaster area. Initial decisions could be made about whether or where a certain location should be taken into further on-site inspection. Then, the Interferometric Synthetic Aperture Radar (InSAR) processing of Sentinel-1 images was performed to define two-dimensional (2D) East-West (E-W) and vertical co-seismic deformation maps near the Zhalang temple. Finally, the measurements obtained by seismic and InSAR methods were validated by unmanned aerial vehicle (UAV) imagery and field surveying. The results showed that: the maximum E-W striking deformation was ∼2.54 cm toward the east and the vertical subsidence was ∼0.01 cm centered on the Zhalang temple, suggesting that the E-W striking deformation significantly affected the surrounding region. Moreover, the spatial heterogeneity indicator of the InSAR deformation maps revealed the locations of underground faults with surface expressions. Further field survey detected surface fractures at Zhalang temple due to secondary effects of the Mw 7.4 earthquake. The genetic process of faulting and fracturing is crucial in terms of hazard assessment and mitigation strategies. In countries with strong environmental and seismic risks, the presented work contributes to the disaster risk reduction (DRR) of heritages in natural-hazard-prone areas and also takes on a social value because it provided supplements for the protection of a heritage that represents the very identity nationwide.

Overall subshear but locally supershear rupture of the 2021 Mw 7.4 Maduo earthquake from high-rate GNSS waveforms and three-dimensional InSAR deformation

An Mw 7.4 left-lateral earthquake hit Maduo County in Qinghai province, China, on 21 May 2021. In this paper, we combined the 1-Hz global navigation satellite system (GNSS) displacement waveforms, GNSS static offsets and the three-dimensional (3D) co-seismic deformation field from the interferometric synthetic radar (InSAR) measurements to estimate the source kinematics of this event. Our results reveal that there was about 160 km of surface ruptures with varying strike angles, and the earthquake propagated bilaterally, with the bulk of the slip formed to the southeast of the epicenter. Substantial slip occurred to a depth of ~6 km, and the estimated maximum slip was ~5 m. The source time function presents a ~ 35-s total duration with two peaks, and the total geodetic seismic moment is 1.61 × 1020 Nm (equivalent to Mw 7.4). The near-field high-rate GNSS waveforms inversion results indicate that this earthquake is an overall subshear but locally supershear rupture event. The preferred average rupture velocity is 2.8 km/s while the velocities to the southeast and northwest of epicenter are 3.8 and 2.2 km/s, respectively. Supershear enhanced ground motion and simulation using the 3D curvilinear grid finite-difference method shows the acceleration caused by the earthquake exceeded the building code limits for bridges that collapsed due to strong ground shaking. Furthermore, this earthquake increased the stress level of the Maqin–Maqu segment of the East Kunlun Fault, and was also responsible for an off-fault aftershock sequence at the northwest end of the earthquake rupture.

Detection of Large Herbivores in UAV Images: A New Method for Small Target Recognition in Large-Scale Images

Algorithm design and implementation for the detection of large herbivores from low-altitude (200 m–350 m) UAV remote sensing images faces two key problems: (1) the size of a single image from the UAV is too large, and the mainstream algorithm cannot adapt to it, and (2) the number of animals in the image is very small and densely distributed, which makes the model prone to missed detection. This paper proposes the following solutions: For the problem of animal size, we optimized the Faster-RCNN algorithm in terms of three aspects: selecting a HRNet feature extraction network that is more suitable for small target detection, using K-means clustering to obtain the anchor frame size that matches the experimental object, and using NMS to eliminate detection frames that have sizes inconsistent with the size range of the detection target after the algorithm generates the target detection frames. For image size, bisection segmentation was used when training the model, and when using the model to detect the whole image, we propose the use of a new overlapping segmentation detection method. The experimental results obtained for detecting yaks, Tibetan sheep (Tibetana folia), and the Tibetan wild ass in remote sensing images of low-altitude UAV from Maduo County, the source region of the Yellow River, show that the mean average precision (mAP) and average recall (AR) of the optimized Faster-RCNN algorithm are 97.2% and 98.2%, respectively, which are 9.5% and 12.1% higher than the values obtained by the original Faster-RCNN. In addition, the results obtained from applying the new overlap segmentation method to the whole UAV image detection process also show that the new overlap segmentation method can effectively solve the problems of the detection frames not fitting the target, missing detection, and creating false alarms due to bisection segmentation.

Blood routine reference value range should be adjusted according to regional and ethnic characteristics.

ObjectiveTo further understand the influence of regional and ethnic factors on blood routine indicators.MethodsThe routine blood test (RBT) results of 617 healthy men aged 18–45 years old of the Li, Tibet, and Han nationalities living in the city of Sanya, Hainan Province (200 m), the city of Xining, Qinghai Province (2,300 m), and Maduo County of Qinghai Province (4,300 m) for a long time were studied. Eight indexes, such as the red blood cell (RBC), hemoglobin (Hb), and platelet (PLT) counts, were compared and analyzed.ResultsWith an increase in altitude, the RBT index values and change trends of the different ethnic groups were different. When the altitude increased by 2,000 m, the RBC and Hb increased by 6.6 and 8.1%, respectively, and the PLT decreased by 16.8%. However, the RBC, Hb, and PLT of the Tibetan subjects decreased by 7.4, 5.1, and 3.0%, respectively. In the same region, there were also significant differences in the RBT index values among the ethnic groups. The RBC increased, Hb decreased, and PLT did not change in the Li nationality in Sanya compared with the Han nationality. The RBC, Hb, and PLT of Tibetans in the Xining area were significantly higher than those of the Han population. Referring to the current RBT reference value range in China, the abnormal rates of the various RBT index values of the enrolled population were high. By utilizing Hb as an example, 27.7% of the Li nationality in Sanya was low, 67.0% of the Tibetan nationality in Xining was high, and 89.4% of the Maduo Han nationality was high. The PLT was lower in the Sanya Li nationality (13.8%) and the Maduo Han nationality (88.3%).ConclusionRegional and ethnic factors have a significant impact on the RBT, and the current range of normal values of the RBT in China needs to be revised and adjusted.

Seismic damage analysis of Yematan Bridge under near-fault earthquakes

On May 22, 2021, a magnitude 7.4 (Ms) earthquake, the largest earthquake in mainland China since the Wenchuan magnitude 8.0 (Ms) earthquake, occurred in Maduo County, Qinghai Province, China. The Maduo earthquake caused significant damage to the Yematan Bridge near the fault and epicenter, which resulted in excessive girders movement and the widespread failure of high damping bearings. The seismic performance of the Yematan Bridge was studied by finite, which simulated the mechanical behavior of the shear key and high damping bearings. To better restore the seismic damage situation, nonlinear analysis is carried out by using two constitutive models of high damping rubber bearings with and without damage. The ground motion input contains near-fault features concluded directivity effect and fling step, and genetic algorithm is used to find the optimal ground motion amplitude for seismic response analysis. The analysis showed that one of the essential reasons for the severe damage to the bridge is that the bridge axis is close to the predominant seismic angle, and the bearing was damaged by the directivity effect. The calculation results obtained by considering the bearing failure constitutive model are closer to the field investigation of earthquake damage. Finally, corresponding seismic measures and suggestions are proposed according to the seismic damage situation and mechanism of the bridge.

Effects of Chronic Hypoxic Environment on Cognitive Function and Neuroimaging Measures in a High-Altitude Population.

ObjectiveThis study aimed to investigate the effects of long-term hypoxic environment exposure on cognitive ability and neuroimaging characteristics in a highland population in China.MethodsHealth system workers in Maduo County (4,300 m above sea level) and Minhe County (1,700 m above sea level) were selected as research participants and divided into a high-altitude (HA) group and low-altitude (LA) group, respectively. Cognitive ability was assessed using the Montreal Cognitive Assessment (MoCA), Verbal Fluency Test (VFT), Symbol Digit Modalities Test (SDMT), Trail Making Test A and B (TMT), Digit Span Test (DST), and Rey Auditory Verbal Learning Test (RAVLT). All participants underwent a magnetic resonance imaging (MRI) scan, resting state functional MRI scan, and diffusion tensor imaging to clarify changes in regional gray matter (GM) volume, anisotropy index (FA), local consistency (ReHo), and low-frequency oscillation amplitude (ALFF).ResultsThe HA group had significantly lower MoCA, DST, VFT, RAVLT, and TMT scores compared to the control group. No significant differences were found in SDMT score. Furthermore, compared to the LA group, the HA group had significantly lower GM density of the left olfactory cortex, right medial orbital superior frontal gyrus, bilateral insula, left globus pallidus, and temporal lobe (left superior temporal gyrus temporal pole, bilateral middle temporal gyrus temporal pole, and right middle temporal gyrus). In terms of FA, compared with the LA group, the HA group had lower values for the corpus callosum, corpus callosum knee, bilateral radiative corona, and left internal capsule. The HA group had lower ALFF values of the left cerebellum, left putamen, left orbital inferior frontal gyrus, and left precuneus, but higher ALFF values of the left fusiform gyrus, bilateral inferior temporal gyrus, left orbital superior frontal gyrus and medial superior frontal gyrus, compared to the LA group. There was no significant group difference in ReHo values.ConclusionOur findings suggest that a chronic hypoxic environment can induce extensive cognitive impairment. Decreased GM density in multiple brain regions, damaged nerve fibers, and unbalanced neuronal activity intensity in different brain regions may be the structural and functional basis of cognitive impairment due to hypoxia.

The 2021 Mw7.4 Maduo earthquake: Coseismic slip model, triggering effect of historical earthquakes and implications for adjacent fault rupture potential

On 22 May 2021 (CST), an Mw7.4 earthquake struck Maduo County, Qinghai Province, China, which was the largest seismic event in China since the 2008 Mw7.9 Wenchuan earthquake. Several scientific questions associated with the event could be addressed: (1) what fault slip model can explain the Maduo earthquake? (2) what effects do historical earthquakes impose on the Maduo earthquake? and (3) what implications does the Maduo earthquake have for future rupture potential of adjacent tectonic faults? So we conduct a comprehensive study to answer the three questions by collecting satellite SAR images, GPS data, seismic waveform data, historical earthquakes, and aftershocks associated with the Maduo earthquake. The estimated fault slip model shows that the Maduo earthquake ruptures two faults in a manner of dominant sinistral strike-slip motion, with slip peaks of ~4.8 m occurring near the surface. The minor fault to the east dips to the south accommodating an obvious reverse slip, well consistent with reverse fault scarps, reverse faulting aftershocks, and significant upward surface displacements immediately south of this branch. Such a reverse slip is probably controlled by the motion of nearby major sinistral strike-slip faults (the Eastern Kunlun fault and the Maduo–Gande fault). Among 32 historical Mw≥ 6.0 earthquakes used in this study, we find that the 1937 Mw7.8 Huashixia earthquake may affect the Maduo earthquake most, delaying its occurrence by decreasing the Coulomb failure stress (CFS) at the hypocenter by > 1 bar and on the entire causative fault by an average of 0.68 bar. Besides, the Mw6.1 Yangbi earthquake, which occurred ~4.5 h ahead of the Maduo earthquake, appears to make little influence on the Maduo earthquake because it hardly perturbates the CFS at the hypocenter of the Maduo earthquake. Furthermore, the cumulative CFS change due to both the 32 historical earthquakes and the 2021 Maduo event indicates that the Tuosuo Lake–Maqu segment of the Eastern Kunlun fault may be at high risk of future rupture.

Interaction between historical earthquakes and the 2021 Mw7.4 Maduo event and their impacts on the seismic gap areas along the East Kunlun fault

On May 21, 2021 (UTC time), an Mw7.4 earthquake struck Maduo County, Qinghai Province, China. The rupture of this typical strike-slip event and its aftershocks along the Kunlun-Jiangcuo fault (JCF) propagated approximately 170 km from the epicenter. In this study, we calculated the coseismic and postseismic Coulomb stress changes induced by 14 historical earthquakes and investigated their impacts on the 2021 Maduo source area. We found that the JCF is in the stress shadow of these historical events with a combined ΔCFS range of approximately − 400 to − 200 kPa. Since the seismogenic fault of the 1937 event is nearly parallel and close to the JCF, the rupture of the 1937 event had the greatest inhibitory effect on Maduo source area. We hypothesize that the actual loading rate at the depth of the seismogenic layer in the Maduo source area is much higher than the simulated value (0.3 kPa/a). Consequently, the Maduo earthquake still occurred despite the considerable delaying effect of these historical earthquakes (especially the 1937 event). Our findings also indicate that the tectonic stress in the eastern Bayanhar block is still rapidly accumulating and adjusting. Our investigation further reveals the enhanced stress induced by the historical and Maduo events with ΔCFS values of approximately 30–300 kPa and 50–300 kPa on the Xidatan-Dongdatan segment (XDS) and the eastern end of the East Kunlun Fault (EKF), respectively, not only on the Maqin-Maqu segment (MMS) but also at the eastern end of each branch segment of the EKF. Hence, considering the accumulation of tectonic stress, we suggest that the seismic hazard in these two regions has been promoted.Graphic

Testing a Prototype Earthquake Early Warning System: A Retrospective Study of the 2021 Mw 7.4 Maduo, Tibet, Earthquake

Abstract On 21 May 2021, an Mw 7.4 earthquake occurred in Maduo County, Qinghai Province, China. A dense network of high-rate (1 Hz) Global Navigation Satellite System (GNSS) stations around the epicenter provided one of the most complete recordings of GNSS kinematic displacements in Tibet to date. We used these data retrospectively to test a prototype earthquake early warning (EEW) system. Here, we present the results of that test, in which the EEW system archived high-rate GNSS displacement streams, and then used them to track evolving magnitude and slip. The geodetic module in the EEW system issued the first alert 34 s after the earthquake onset. The first alert had a moment magnitude (Mw) of 6.65, which then increased until reaching a stable value (Mw 7.4) 61 s after the earthquake onset. Testing results show good agreement with rapid GNSS displacements and postprocessed GNSS displacements; moreover, the rapid finite-fault inversion is consistent with postinversion magnitude and rupture dimensions. Our findings confirm the viability and usefulness of this EEW system in quasi-real-time magnitude estimation and finite-fault slip inversion.

Tibetan Herders’ Life Satisfaction and Determinants under the Pastureland Rehabilitation Program: A Case Study of Maduo County, China

The Pastureland Rehabilitation Program (PRP) has been implemented for nearly 20 years, and the lives of herders in different regions have been affected to varying degrees. The level of people’s well-being could measure the success of policy. Taking Maduo County as an example, the life satisfaction of 266 Tibetan herders was investigated through a participatory questionnaire survey in July 2021. Multiple linear regression and optimal scale regression were constructed to analyze the impact of the satisfaction of different aspects of life and PRP on life satisfaction, respectively. The results show that the herders in Maduo County had relative high satisfaction in various aspects of life and overall life, and leisure and consumption were important aspects influencing life satisfaction. The relative living standard, the difficulty in borrowing and the quality of government services had a significant positive impact on herders’ life satisfaction. Occupation and migration location also led to the significant differences of life satisfaction. However, the income changes caused by PRP and subsidy levels did not show a significant impact. We discussed the particularity of Maduo County and suggested that more attention should be paid to the improvement of the social environment such as wealth disparity, channels of assistance, working environment, and the effective assistance formulated according to the demands of different groups needs to be optimized continuously, so as to enhance the self-development ability of herders.