Journal of Seismology最新文献

On December 27, 2022, a moderate earthquake (M_L = 5.0) struck the western coast of the Gulf of Suez at 28.03° N and 33.47° E. The event was felt up to 500 km away and was recorded by the Egyptian National Seismological Network (ENSN) and the Egyptian National Strong Motion Network (ENSAN). The epicenter was located about 53 km from a previous M_L = 5.1 earthquake that occurred in June 2013. This study determines the source parameters, focal mechanism, and moment tensor of the December 27, 2022 earthquake to better understand its rupture characteristics and tectonic context. Displacement spectra were analyzed to estimate the long-period spectral level and corner frequency, from which the seismic moment was derived (1.96 × 10²⁰–1.44 × 10²² dyne·cm) and converted to moment magnitude. The estimated source radius ranged from 136 to 254 m, with stress drop values between 2.3 MPa and 61.3 MPa. The corner frequency, inversely related to rupture duration, varied from 5.2 Hz to 9.8 Hz. Moment tensor analysis of the mainshock and three aftershocks (M_L ≈ 4.0) revealed predominantly normal faulting with minor strike-slip components, aligned mainly along NNW–SSE and NW–SE directions. This mechanism is consistent with the regional tectonic framework and previously reported fault structures of the Gulf of Suez. The results contribute valuable information for updating seismic hazard assessments in this economically strategic region.

In this research, we used the 2006–2024 seismic catalog from the Iranian Seismological Center for a comprehensive analysis of the seismicity parameters (b -value, the magnitude of completeness (M_C), Fractal Dimension (D_C), Seismic Moment (M₀), and seismic quiescence (Z -value)) in the vicinity of Mw 6.2 Murmuri Earthquake of August 18, 2014, in the Zagros region of Iran. The M_C exhibits spatial heterogeneity, with values ranging from 2.0–2.5 near Dehloran to 3.0–3.5 near the Mountain Front Fault (M.F.F.), reflecting detection challenges in complex fault zones. Spatial b -value distribution indicates low values near the mainshock epicenter and M.F.F., suggesting high-stress accumulation. The D_C -value shows higher values near the epicenter, reflecting clustered seismicity. An orthogonal regression analysis reveals a strong negative correlation (r = -0.71) between b-value and D_C -value in the region. The Z -value distribution in early 2014, using a 2-year time window, identifies significant quiescence near the epicenter, a precursor to the mainshock, transitioning to post-event activation. The spatial distribution of Z -values exhibits a complex pattern, with lower values (z ≈ − 1.0 to − 1.5) concentrated near the Murmuri epicenter, indicating a moderate decrease in seismic activity relative to the reference period. These findings highlight the M.F.F. as a high-hazard zone, with integrated parameter analysis enhancing precursory detection and post-event stress mapping.

The high pressure Guwahati–Siliguri Pipeline (GSPL) passes through the densely populated Guwahati city in northeast India. This study evaluates response of the GSPL segment within Guwahati city with a focus on the effect of seismic wave induced failure. Seismic sources within a 500 km radius of the Guwahati city are identified and classified into four seismic source regions of (1) Shillong Seismogenic Zone (SSZ), (2) Indo-Burmese Orogenic Front (IBOF), (3) Bengal Deltaic Seismic Block (BDSB), and (4) Eastern Himalayan Seismotectonic Belt (EHSB). The b-values are 1.00 ± 0.03 (SSZ), 1.03 ± 0.02 (IBOF), 0.66 ± 0.06 (BDSB), and 0.93 ± 0.02 (EHSB), indicating elevated seismic activity in BDSB. Deterministic Seismic Hazard Assessment (DSHA) reveal Oldham fault as the source for high level of ground shaking. Peak Ground Accelerations at bedrock level (PGA_b) obtained from DSHA range between 0.219 g to 0.239 g. Probabilistic Seismic Hazard Assessment (PSHA) results reveal that for 2% probability of exceedance in 50 years the PGA_b range between 0.202 g to 0.242 g. At 10% probability of exceedance in 50 years the PGA_b range between 0.126 g to 0.146 g. Hazard curves identify Kopili fault as the contributor for high levels of ground motion at Guwahati city. Further, the study shows that the cumulative strain experienced by the GSPL as a result of tension against axial strain due to seismic wave passage remains below the allowable limit of 3% for worst case scenario, 2% probability of exceedance in 50 years as well as 10% probability of exceedance in 50 years.

On January 7, 2025, an Ms 6.8 earthquake struck Dingri County, Shigatse, Tibet Autonomous Region, causing severe casualties and property losses. This study utilized Sentinel-1 satellite data and Interferometric Synthetic Aperture Radar (InSAR) technology to obtain the co-seismic surface deformation field, invert the fine geometric parameters and slip distribution of the seismogenic fault, and calculate regional co-seismic Coulomb stress changes. Results show that both ascending and descending orbit radar satellites captured the co-seismic deformation, with a field range of 160 km × 100 km and surface rupture of the seismogenic fault. The maximum Line-of-Sight (LOS) deformations were -1.73 m (ascending) and -1.26 m (descending), while azimuth deformations reached -1.11 m and -1.10 m, respectively. Three-dimensional deformation revealed significant subsidence (1.69 m vertical) on the west-side hanging wall and uplift (0.22 m max) on the east-side footwall, indicating normal fault movement along the Dengmocuo Fault. Inversion constrained by InSAR data showed the fault is 32 km long, 14 km wide, with a strike of 187°, dip angle of 56°, and slip angle of -68°, rupturing mainly at 0–16 km depth. The maximum slip was 3.93 m, seismic moment 4.03 × 10¹⁹ N·m, and moment magnitude Mw 7.04. More than 80 aftershocks with M ≥ 3.0 near the Dengmocuo fault were mainly caused by the increase in Coulomb stress caused by the Dingri Mw7.04 earthquake. Considering the influence of historical earthquakes and background tectonic stress, the Coulomb stress change value of the Dingjie County seat will increase by 0.01 MPa after 2047, indicating the possibility of earthquakes occurring. The increase in Coulomb stress change value in the county seat of Gangba is greater than 0.3 MPa, indicating a high possibility of earthquake occurrence.

We used accelerograms from foreshocks recorded by the closest strong-motion stations to the epicentral location of the 2010 El Mayor-Cucapah earthquake (Mw7.2) to estimate S-wave near-source attenuation and to investigate the spatial–temporal evolution of the spectral decay parameter kappa (κ). We found that κ estimated from the foreshocks has significantly higher values compared with those estimated using the mainshock recordings. Since κ is inversely proportional to the quality factor Q and this may vary depending on the state of stress and the presence of fluids, this observation indicates that Q was higher in the epicentral region during the mainshock rupture process, probably due to a higher concentration of stress. We calculated the average regional S-wave attenuation (widetilde{kappa }(r)) before and during the mainshock using a nonparametric approach, and we also found higher attenuation before the occurrence of the main event, suggesting a possible role of fluid flow in the rupture process of the main rupture. Before and during the mainshock (widetilde{kappa }(r)) increased with increasing hypocenter distance, but at short distances (r < 17 km) (widetilde{kappa }(r)) increased faster before the main shock. However, during the main rupture (widetilde{kappa }(r)) increased faster than during the foreshock sequence for r > 17 km, suggesting that the tectonic stress probably decreased beyond that distance. 17 days before the mainshock the near-source attenuation (({kappa }_{s})) was very low in the ruptured area, ({kappa }_{s}=0.0374) s, increasing during the next 30 h to ({kappa }_{s}=) 0.0490 s, then ({kappa }_{s}) started to decrease to the value of ({kappa }_{s}=0.0024) s during the occurrence of the main event. We interpret this decrease in ({kappa }_{s}) as due to increasing Q resulting from an important increase of tectonic stress before the occurrence of the Mw7.2 earthquake. We conclude that κ, in combination with other geophysical parameters, it is useful to understand the preparatory phases of the earthquake rupture process.

The three fault zones of Longmenshan, Xianshuihe, and Anninghe‒Zemuhe & Daliangshan, which constitute the large-scale fault system in western Sichuan, China, were selected as the research objects for statistical analyses and mining of the underlying regularities in seismic event records. In this study, earthquake catalogues from 1970–2023 were collected, the Gutenberg-Richter (G‒R) relation was fitted, the seismicity was analysed, and the magnitude of completeness (Mc) was obtained. According to Mc, the earthquake catalogue of each fault zone was divided into three groups of data according to magnitude: M ≥ 3.0 (complete magnitude group), M = 3.0 ~ 4.4 (low-magnitude group), and M ≥ 4.5 (high-magnitude group), and time series of seismic frequencies were established. Multiple nonparametric testing methods were subsequently used to statistically infer and analyse the differences in the time series of seismic frequencies among different fault zones. There were significant differences among all the series, with the exception of the high-magnitude group of the Longmenshan fault zone and the low- and high-magnitude groups of the Xianshuihe fault zone. Furthermore, the Pearson correlation coefficient and cross-correlation functions (CCF) among the series of each fault zone are calculated. There were different degrees of synchronous or lagged (delayed) effects among the complete magnitude groups, low-magnitude groups, and high-magnitude groups of different fault zones. On the basis of these differences and correlations, multiple linear stepwise regression equations were applied to establish correlation models that quantitatively characterize the correlations among the seismic frequencies of the three fault zones, and practical explanations were given to reveal the seismic correlation relationships and regularities. This study provides not only references for earthquake prevention and disaster reduction in the research area but also research ideas and approaches for similar analyses of the seismic differences and correlations among adjacent fault zones in large-scale fault systems.

On January 7, 2025, a Mw 7.1 earthquake struck Southern Tibet, causing significant damage and loss of life. The earthquake and its aftershocks were widely felt across South Asia. This study investigates the seismotectonic characteristics of the event by analyzing its focal mechanism solution, stress tensor inversion, and Coulomb stress changes. The focal mechanism solution was determined using the ISOLA software with full waveform inversion data from the broadband seismometer in Mizoram, Tripura, India, and Tibet, China. Results indicate a normal faulting mechanism with a NNW-SSE strike. An iterative stress tensor inversion using 52 focal mechanism solutions (Mw > 5) from 1976 to 2025, including the Mw 7.1 mainshock, suggests an E-W extensional and nearly N-S compressional stress regime, confirming the regional tectonic influences. Coulomb stress change analysis indicated a stress perturbation ranging from -5 bars (-0.5 MPa) to + 5 bars (+ 0.5 MPa). These stress changes align with the aftershock distributions, suggesting a strong influence of stress transfer. This study contributes to a broader understanding of earthquake interactions in the region and seismic hazard assessment.