pure and applied geophysics最新文献

The lightning flash frequency (LFF, also referred to as lightning flash rate) in four models from the Coupled Models Intercomparison Project, phase 6 is examined. For the present day (PD, 1995–2014), the models exhibit very divergent simulation of LFF in terms of multi–annual averages, interannual variability, and temperature sensitivity. The global mean multi–annual average flash frequency differs by a factor of two between the models, and only two of four models are within the reasonable distance from the LIS/OTD (Lightning Imaging Sensor/Optical Transient Detector) satellite retrievals. The model–data and inter–model differences are even more pronounced at a regional scale and during northern summer. CMIP6 simulations show a general increase in lightning flash frequency from the present day to the late 21st century, especially for the simulations with higher anthropogenic (textrm{CO}_2) emissions into the atmosphere. LFF sensitivity coefficient (beta), which is based on differences between PD and the late 21st century are positive over most continental areas with typical values from 10 to (20 {% , textrm{K}^{-1}}) for annual mean LFF and from 20 to (60 {% , textrm{K}^{-1}}) for JJA averages over the northern extra–tropical continents (and even up to (100 {% , textrm{K}^{-1}}) in some regions for individual models). At the global scale and for annual averages, this sensitivity is from 5 to (17 {% , textrm{K}^{-1}}). In addition, this sensitivity is markedly different from its counterpart derived from the regression of LFF on surface air temperature for PD period. The latter counterpart is negative at the global scale and changes sign between different regions (i.e, it is positive over the North America south–east and is negative over the south–western part of North America and over the India Peninsula). These regional peculiarities are reasonably simulated by the models.

This paper presents a broad spectrum of factors that have an impact on the environment once underground mines have been closed, with particular emphasis on hard coal mines. Based on the review of scientific literature and own experience, several types of environmental impacts of closed mines were specified. In the author’s opinion, sinkholes pose the most serious hazard to post-mining areas. A high degree of urbanisation of the Upper Silesian Coal Basin and a wide range of mining operations conducted in the past necessitate the post-mining areas development for construction purposes. However, investing in these areas cannot carry risks and pose a threat to public safety. Therefore, a simplified method of determining the probability of sinkhole formation depending on the depth of a shallow void (excavation) in the rock mass was proposed. An algorithm has also been proposed for determining the contribution of individual mining companies to causing sinkhole hazard, which is of great importance in legal proceedings.

On December 18, 2023, an M6.2 earthquake shock the Jishishan County (JSSEQ) in the NE Tibetan plateau. In this study, we conducted a comprehensive analysis based on focal mechanism, seismic b-value and local S-wave splitting analysis to investigate the seismogenic structure and stress state associated with the JSSEQ. The focal mechanism solution shows that the JSSEQ occurs at a centroid depth of 13 km and is associated with a node plane dipping to NNE and the other node plane dipping to WSW. The JSSEQ and its aftershocks are dominated by thrust faulting under prominently sub-horizontal WSW-ENE compression, consistent with the regional stress field. We also observe the JSSEQ occurred in the periphery of a low b-value anomaly body and a ~ 2 year decrease of b-value surrounding the mainshock before the occurrence of JSSEQ. The fast directions are sub-parallel to the maximum horizontal compressive stress with an anticlockwise rotation to the north of the Daotanghe-Linxia fault. Combined with the InSAR observation and surface geology, we deduce that the JSSEQ occurred on a highly stressed asperity of a blind NNE-dipping seismogenic fault, under the control of northeastward expansion of the Tibetan plateau. Our results provide important information for understanding the seismogenic structure and dynamic background of this earthquake that occurred in a highly concerned region.

The blind and exposed salt domes in the Fars Arc of the south-eastern Zagros Fold and Thrust Belt, are rooted in the Precambrian–Early Cambrian Hormuz Salt, which deposited over a Precambrian crystalline basement. To define the subsurface blind salt domes and examine the influences of the basement morphology on the distribution of the salt domes and their impact on hydrocarbon accumulation, we used high–resolution terrestrial magnetic and gravity data. Applying various derivative–based filters on the Bouguer gravity anomalies we identified seven blind salt domes. From those, two have characteristic topographic implications and another three have been also imaged by the earlier seismic studies. A low Bouguer anomaly with a prominence sharp variation limits the western extent of the overlying allochthonous Late Oligocene–Early Miocene Fars Salt layer. The horizontal derivative of the Bouguer anomaly highlights a distinctive lineament in the south of the Bander–e–Lengeh anticline, which is interpreted as the effect of the Fars Salt layer on folding and faulting propagation. The magnetic anomalies were not effective for detecting blind salt domes due to the presence of highly magnetised crystalline basement rock fragments within salt domes, yielding an unexpected non-zero susceptibility value similar to the surrounding sedimentary layers. This indicates the influence of crystalline basement dynamics on salt tectonism in the study area. The N–S trend of the long-wavelength magnetic anomaly of the Hendurabi Lineament extends east of the study area and reflects a basement structure. The integrated E–W gravity–magnetic forward modelling implies an N–S trending horst–graben structure in the crystalline basement, which controls the thickness of the Hormuz salt and possibly the distribution of salt domes.

In the controlled source radiomagnetotelluric (CSRMT) sounding method, different types of sources are in common use. However, no systematic examination of their advantages and disadvantages exists. In this paper, we analyze the electromagnetic fields of different CSRMT sources: horizontal electric dipole, HED, horizontal magnetic dipole, HMD, and vertical magnetic dipole, VMD, using both numerical modelling and field data. Positions of the boundary between the far-field and transition zones have been determined. Using 1D and 2D modelling and results of field experiments, we have shown that the HMD source has the smallest transition zone, while the VMD source has the largest one. In general, the HMD and HED sources are preferred for soundings in the far-field zone, due to the versatility of the transmitter’s geometry, and to the possibility of tensor measurements and use of 2D-3D magnetotelluric codes for data interpretation. In the case of the homogeneous half-space, for all sources the boundary between the transition and the far-field zone is farther away from a source for the impedance phase than for the apparent resistivity. Comparison of the signal magnitudes’ decay indicates that the field from the VMD source shows the slowest decrease with distance in the transition zone, while the field from the HMD source shows the fastest decrease, confirming the shorter range of measurements using the latter source. Using field experiments, we have compared the magnitudes of HED-, VMD-, and HMD-signals at odd subharmonics relative to the signal magnitude at the main frequency. We find that use of a HED source has definite advantage over loop sources for broadband frequency measurements with the square waveform from transmitter.

The Crati valley (Calabria, Italy) is a densely populated area characterized by high seismic hazard, as inferred from the strong earthquakes that occurred in the past centuries and from the tectonic structures that border the graben. The valley extends in the NS direction between Sila massif to the east and Catena Costiera to the west. In recent years the area has been characterized by low to medium magnitude earthquakes, mostly located in the upper crust. In this work we analyzed local and regional earthquakes and seismic noise to study the seismic response and the upper crust structure in the investigated area. We analyzed 12 h of seismic noise and 24 regional earthquakes to compute the horizontal-to-vertical spectral ratio (HVSR) at all seismic stations available in the area. Results show that the two sites located on the sediments within the low-velocity anomaly are characterized by a high HVSR peak of amplitude 4 at frequency of about 0.27 Hz, which likely corresponds to the seismic resonance of the sediment-filled basin. At the same two sites, the amplification factor computed with the Standard Spectral Ratio (SSR) method applied to regional earthquakes shows values up to 6 in the frequency range 0.3–1.0 Hz. We used a selection of 332 local earthquakes in the magnitude range 0.6–4.4 to compute a high-resolution P-wave 3D velocity model of the Crati valley and surrounding terranes. The tomographic analysis shows results with a good resolution down to at least 15 km depth. A strong low-velocity anomaly at shallow depths in the well resolved sector of the valley coincides with the sediment-filled graben, the most important geological feature of the area. The results of this work provide a valuable information to be considered in the estimation of local seismic hazard.

The urbanization and frequency of extreme rainfall events (EREs) have considerably increased over the recent decade in several cities in India. Forecasting of these EREs remains a significant challenge not only in urban environments but also across diverse geographical regions. However, there is a particularly pressing need for improved rainfall forecasts in urban areas where the impacts of cities and human activities are profound. Using the Weather Research and Forecasting (WRF) model, a series of sensitivity experiments have been carried out by changing the various parameterization schemes to establish an improved model configuration for predicting EREs across the city of Bhubaneswar, Odisha- one of the most vulnerable cities to heavy rainfall in the recent decades. The study examines the influence of the urban heat island (UHI) effect on EREs, focusing on two specific EREs that occurred over Bhubaneswar and neighboring regions during the summer and post-monsoon season on July 19–21, 2018, and October 19–21, 2017. A total of thirty-two combinations of various cumulus, microphysics, and land surface sensitivity experiments are carried out for each ERE (a total of 64 for the two events). The results show that the combinations of Noah +  + Nocumulus and Noah-MP + Thompson + Kain-Fritsch are the most effective in capturing the spatial and temporal patterns of EREs with a root mean square error of 33.9 and 36.2 mm, respectively. In addition, the study successfully reproduced vertical integrated specific humidity. Moreover, it has been observed that the UHI effect reduces rainfall intensity by 4% within urban areas during extreme rainfall events.

The Four-Dimensional Variational (4DVar) data assimilation system of the Advanced Research Weather Research and Forecasting (WRF) model, developed by the international community dedicated to data assimilation research and operations, is customised to simulate the super cyclonic storm "Amphan" formed over the Bay of Bengal during May 16, 2020, to May 21, 2020. Five simulations are conducted using five different microphysics schemes namely, Kessler, Lin et al., WRF Single Moment 3-class (WSM3), WSM5, and WSM6 at a horizontal resolution of 18 km, keeping the Kain–Fritsch cumulus and the Yonsei University planetary boundary-layer scheme fixed. The model simulated features of "Amphan" are compared with observational data from the India Meteorological Department (IMD), the Global Precipitation Measurement mission (GPM), and the 5th generation European Centre for Medium-Range Weather Forecasts (ECMWF) Atmospheric Reanalysis (ERA-5) over the specified region. Among all the schemes, Lin et al. scheme shows track remarkably close to the observed track. Lin et al. (WSM5) scheme shows least along track (AT) error of 7.47 km at 24-h forecast length. Lin et al. shows least AT error of 5.8 km (28.12 km) for 48-h (72-h) forecast length. All schemes except Kessler and WSM3 show the spatial distribution of maximum sustained wind (MSW) surrounding the eye of the cyclone which is similar with ERA5 data. All the schemes underestimate the 10m-MSW during the entire life of the storm. However, the Kessler scheme simulates higher 10m-MSW during 00 UTC 18 May to 12 UTC 19 May in comparison to other schemes and further the simulated MSW matches with IMD observation up to 06 UTC 20 May. The Kessler scheme overestimates the MSLP for the intensity level ESCS-VSCS-SCS-CS valid 09 UTC on 19 May to 00 UTC on 21 May and other schemes underestimate during this period. The analysis carried out with the Method for Object-Based Diagnostic Evaluation tool reveals that the Lin et al. (WSM6) scheme indicates enhanced forecast proficiency for accumulation valid 00 UTC 20 May (21 May) 2020. The analysis of vertically integrated moisture transport (VIMT) and vertically integrated moisture divergence (VIMD) suggests that the greater moisture transport is quite evident in Lin et al. scheme during the SuCS intensity level. Kessler scheme is efficient in simulating warm-rain process and high intensity storm.

The article investigates the reliability of moment tensor (MT) inversion in time domain with use of first P-wave amplitude, a method used to determine the source mechanisms of earthquakes, across four different seismic networks. The study compares the synthetic tests results of MT inversion for two underground mining and two artificial reservoir monitoring seismic networks. The analysis was performed to assesses how consistency and accuracy of the results depend on different factors like: network configuration, events depth, velocity model, focal mechanism of event and applied noise. The findings highlight the impact of network configuration compared to other variables and data quality on the reliability of moment tensor inversion and provide insights into different factors which have to be considered to enhance MT accuracy. The significance of events depth in P-wave amplitude MT inversion and the necessity to consider velocity model influence, especially presence of high velocity gradient, is highlighted by the presented results.