Earthquake Research Advances最新文献

Laboratory experiments and numerical simulations on rock friction perturbations, an important means for understanding the mechanism and influencing factors of stress-triggered earthquakes, are of great significance for studying earthquake mechanisms and earthquake hazard analysis. We reviews the experiments and numerical simulations on the effects of stress perturbations on fault slip, and the results show that stress perturbations can change fault stress and trigger earthquakes. The Coulomb failure criterion can shed light on some questions about stress-triggering earthquakes but cannot explain the time dependence of earthquake triggering nor be used to investigate the effect of heterogeneous stress perturbations. The amplitude and period are important factors affecting the correlation between stress perturbation and fault instability. The effect of the perturbation period on fault instability is still controversial, and the effect of the high-frequency perturbation on earthquakes may be underestimated. Normal and shear stress perturbation can trigger fault instability, but their effects on fault slip differ. It is necessary to distinguish whether the stress perturbation is dominated by shear or normal stress change when it triggers fault instability. Fault tectonic stress plays a decisive effect on the mode of fault instability and earthquake magnitude. Acoustic emission activity can reflect the changes in fault stress and the progression of fault nucleation, and identify the meta-instability stage and precursor of fault instability, providing a reference for earthquake prediction.

In this study, we used high-resolution optical satellite images on the Google Earth platform to map large-scale landslides in Xianyang City, Shaanxi Province, China. After mapping, a comprehensive and detailed large-scale landslide inventory that contains 2924 large-scale landslides was obtained. We analyzed the spatial distribution of landslides with seven influencing factors, including elevation, slope angle, aspect, curvature, lithology, distance to a river, and distance to the fault. Landslide Number, Landslide Area, Landslide Number Density (LND), and Landslide Area Percentage (LAP) were selected as indexes for the spatial distribution analysis. The results show that the number and area of landslides in the elevation range of 1000–1200 ​m is the highest. The highest number of landslides was observed in the slope angle of 25°–30°. North-facing slopes are prone to sliding. The area and number of landslides are the largest when the slope curvature ranges from −1.28 to 0. The LND and LAP reach their maxima when the slope curvature is less than −2.56. Areas covered by the Tertiary stratum with weakened fine-grained sandstone and siltstone show the highest LND and LAP values. Regarding distance to a river, the LAP peaks in the range of 300–600 ​m, whereas the LND peaks in an area larger than 2100 ​m. The values of LND and LNP rise as the distance from the faults increases, except for the locations 30 ​km away from active faults. This phenomenon is because active faults in this area pass through the plain areas, while landslides mostly occur in mountainous areas. The cataloging of landslide development in Xianyang City provides a significant scientific foundation for future research on landslides. In addition, the spatial distribution results are useful for landslide hazard prevention decisions and provide valuable references in this area.

The Anninghe fault is a major left-lateral strike-slip fault in southwest China and a seismic gap with a potential earthquake larger than M_W 7.0 lies in the Mianning-Xichang segment according to recent observations. The shallow structure of this region can offer a glimpse into the geometry of the fault, which plays an important role in earthquake hazard mitigation. To further investigate the sedimentary structure of the Anninghe fault zone, two dense linear arrays with a station spacing of around 80 ​m were deployed across the fault. In this study, the H/V spectral ratio (HVSR), together with its peak frequency at each station site, was obtained by applying the Nakamura method. Our findings demonstrate that the peak frequency behaves in high correlation with lithology and is controlled by topography. HVSR in foothills or regions with magmatic intrusion shows a single peak at about 2–3 ​Hz. In locations with abundant Quaternary sedimentation, such as Anninghe valleys and fracture zones, another low-frequency peak around 0.4 ​Hz can be noticed in HVSR. By using the empirical relationship, the thickness of the sedimentary layer around the fault fracture zone is estimated to be 300–600 ​m. Furthermore, the sedimentary interface shows a downward dip to the east, possibly influenced by the east-west extrusion stress. Considering the resonance effect, buildings with 6–9 stories in the valley area of the Anninghe require additional attention in earthquake hazard prevention.

The Litang fault (LTF), located in the southeast of the Qinghai-Tibetan Plateau, is known for its high level of present-day seismicity, whereas its Pleistocene activity has been scarcely documented. This study focused on a tract of banded travertine deposits precipitated from thermal waters along the NW–SE-trending LTF trace. The role of travertine deposits in recording neotectonic activity has been studied by identifying their internal structure. Typical soft-sediment deformation structures observed within the banded travertines include micro folds, liquefied breccia, and liquefied diapirs. These deformed structures, which are restricted to a single unit separated unconformably by undeformed layers, can be traced for tens of meters, indicating that they were formed by seismic shaking triggered by LTF activity. The deformation of the banded travertine layers is attributed to the combined effects of seismic shaking, liquefaction, and fluidization, and it can be related to a paleo earthquake event with a magnitude of M_S ​> ​5. The U-series ages obtained from the banded travertine deposits perturbed by the earthquakes are in the range of 130.59–112.94 ka, indicating an important fault-assisted neotectonic activity that occurred during the Middle–Late Pleistocene. Analysis of such structures, in combination with the use of U-series dating methods, can yield a reliable timing of neotectonic activity and provide new evidence for understanding the seismotectonic setting of the Litang area.

The Antarctic ice sheet is an important target of Antarctic research. Thickness and structure, including intraice and subice, are closely related to the mass balance of the ice sheet, and play an important role in the study of global sea level and climate change. Subglacial topography is an important basis for studying ice sheet dynamics and ice sheet evolution. This paper briefly reviews the geophysical detection methods and research status of the Antarctic ice sheet: (1) Conventional methods such as ice radar are the main methods for studying the ice sheet today, and passive source seismic methods such as the receiver function method, H/V method and P-wave coda autocorrelation method have good development prospects; (2) the high-resolution (1 ​km) ice thickness and subglacial topographic database BEDMAP2 established based on various data has greatly improved the ability to detect internal isochronous layers, anisotropic layers, and temperature changes within ice and has advanced research on ice sheet evolution; and (3) ice radar, numerical simulation and core drilling are the main methods to study subglacial lakes and sediments. More than 400 subglacial lakes have been confirmed, and more than 12 000 simulation results have been obtained. Research on the Antarctic ice sheet faces enormous challenges and is of great urgency. Aiming at hot issues, such as Antarctic geological evolution, glacial retreat, ice sheet melting and their relationships with global climate change, it is the frontier and trend of future Antarctic ice sheet research to carry out multidisciplinary and multicountry comprehensive geophysical exploration based on the traditional ice radar method combined with passive seismic methods, especially new technologies such as short-period dense array technology, unmanned aerial vehicles and artificial intelligence. This is expected to further promote Antarctic research.

Geodetic observations have shown that there exist large differences in the viscosity of the deep lithosphere across many large strike-slip faults. Heterogeneity in lithospheric viscosity structure can influence the efficiency of stress transfer and thus may have a significant effect on the earthquake cycle. Until now, how the lateral viscosity variation across strike-slip faults affects the earthquake cycles is still not well understood. Here, we investigate the effects of across-strike viscosity variation on long-term earthquake behaviors with a three-dimensional strike-slip fault model. Our model is a quasi-static model which is controlled by the slip-weakening friction law and power-law rheology. By comparing with the reference case, we find that low viscosity on one side of the fault results in a smaller rupture area but with a higher Coulomb stress drop on the ruptured fault region. In addition, low viscosity also leads to a small Coulomb stress accumulation rate. These combined effects increase the earthquake recurrence interval by approximately 10% and the earthquake moments by about 30% when the low viscosity is related to a geothermal gradient of 30 ​K/km. In addition, across-strike viscosity variation causes asymmetric interseismic ground surface deformation rate. As the viscosity contrast increases, the difference in the interseismic ground surface deformation rate between the two sides of the fault gradually increases, although the asymmetric feature is not pronounced. This asymmetry of interseismic ground deformation rate across a strike-slip fault is supposed to result in asymmetric coseismic deformation if the long-term plate motion velocity is invariant. As a result, this kind of asymmetry of interseismic deformation may influence the evaluation of potential earthquake hazards along large strike-slip faults with lateral viscosity contrast.

Traditional visual interpretation is often inefficient due to its excessively workload professional knowledge and strong subjectivity. Therefore, building an automatic interpretation model on high spatial resolution remote sensing images is the key to the quick and efficient interpretation of earthquake-triggered landslides. Aiming at addressing this problem, a landslide interpretation model of high-resolution images based on bag of visual word (BoVW) feature was proposed. The high-resolution images were pre-processed, and then BoVW feature and support vector machine (SVM) was adopted to establish an automatic landslide interpretation model. This model was further compared with the currently widely used Histogram of Oriented Gradient(HoG) feature extraction model. In order to test the effectiveness of the method, typical landslide images were selected to construct a landslide sample library, which was subsequently utilized as the foundation for conducting an experimental study. The results show that the accuracy of landslide extraction using this method reaches as high as 89%, indicating that the method can be used for the automatic interpretation of landslides in disaster-prone areas, and has high practical value for regional disaster prevention and damage reduction.

On September 5, 2022, at Beijing time 12:52 p.m., an M_S 6.8 earthquake struck Luding County, Garze Tibetan Autonomous Prefecture, Sichuan Province. The epicenter of the earthquake was at the intersection of the Sichuan-Yunnan, Bayankala, and South China blocks. The tectonic background is extremely complex, and strong earthquakes occur frequently. Based on a predetermined focal location and focal mechanism solution for the earthquake, we reversed the focal depth and rupture process of the earthquake by fitting the teleseismic P and SH waves recorded by the global seismic network. The results show that the focal depth is 16 ​km, with the main rupture having a length of about 45 ​km near the epicenter, with a maximum displacement of 1.02 ​m. Although the rupture mainly propagates from the north–northwest (NNW) to the south–southeast (SSE) along the fault strike, there is a small-scale rupture slip zone at shallow depths in the north–northeast (NNE) direction along the epicenter of the seismogenic fault. This rupture image corresponds to the cluster distribution of aftershocks in the NNW and SSE directions starting from the epicenter, corresponding to the distribution of recorded landslides. The earthquake occurred on the Moxi fault, located in the southeastern section of the Xianshuihe fault. The major tectonic feature in this area is the southeastward movement of the Chuandian block relative to the Bayanhar block.

Piezoelectric material, as one of the great potential materials, had attracted lots of attention all over the world due to its distinguish advantages. In this paper, the development of piezoelectric-based technology for application in the field of civil structural health monitoring (CSHM), was summarized and discussed. Based on the different identification mechanisms, the piezoelectric transducer-based technology can be divided into two main approaches as the active or passive sensing and detection methods. This paper summarized the development of these two approaches and discussed their applications in the area of civil structural health monitoring, such as structural and concrete engineering, bridge engineering, pipeline engineering, protection engineering for geological hazards and earthquake disasters, and so on. In addition, the electrical mechanical impedance (EMI) technique, as one of the active identification methods, was also detailly presented. Finally, its great potential for the piezoelectric-based technique was presented based on the detail discussion, especially in the areas of civil structural health monitoring.

We measure spatio-temporal variations of seismic velocity changes in Salton Sea Geothermal Field, California based on cross correlations of daily seismic traces recorded by a borehole seismic network from December 2007 to January 2014. We find clear co-seismic velocity reductions during the 2010 M 7.2 ​El Mayor–Cucapah, Mexico earthquake at ∼100 ​km further south, followed by long-term recoveries. The co-seismic reductions are larger with longer post-seismic recoveries in higher frequency bands, indicating that material damage and healing process mostly occurred in the shallow depth. In addition, the co-seismic velocity reductions are larger for ray paths outside the active fluid injection/extraction regions. The ray paths inside injection/extraction regions are associated with smaller co-seismic reductions, but subtle long-term velocity increases. We also build 3D transient water flow models based on monthly injection/extraction rates, and find correlations between several water flow parameters and co-seismic velocity reductions. We interpret the relative lack of co-seismic velocity changes within the geothermal region as unclogging of fracture network due to persistent fluid flows of geothermal production. The long-term velocity increase is likely associated with the ground water depletion and subsidence due to net production.