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Full waveform inversion (FWI) plays a central role in the field of exploration geophysics due to its potential in recovering the properties of the subsurface at a high resolution. A starting model with ample long wavelength components is essential for the success of most FWI algorithms. Reflection waveform inversion (RWI) is one popular way to invert for the long wavelength velocity components from the short offset seismic data by decomposing the gradient of FWI into migration and tomographic terms. However, the transmitted part of Born scattering in conventional RWI still produces high-wavenumber artifacts, which would hinder its convergence. Thus, in this letter, an efficient nontransmission energy norm Born scattering is used in RWI to overcome the drawbacks of conventional RWI. Finally, we use numerical examples to show that the energy norm Born scattering can provide clean reflection energy from the reflector and enhance the low-wavenumber information in the RWI gradient.

Spectral induced electric polarization provides useful information on geoelectric parameters, which may allow mineral discrimination in exploration geophysics. Electromagnetic coupling between current and potential electrodes equally contributes to understanding the geology but represents the main source of noise in spectral induced electric polarization surveys. In this article, we propose an integrated analysis of these two phenomena in the context of complex resistivity data in order to evaluate their role in exploration geophysics taking into account their specificities. Deepening previous studies of forward modeling and inversion of mutual impedance in the frequency domain, in this present approach, we have employed an expanded apparent complex resistivity function, which includes the inductive effect in its parameters. We developed an integrated inversion of this function using the very fast simulated annealing and least-squares methods to estimate the geoelectric parameters. We also performed tests and applications on synthetic and real data, discussing the benefits of using the proposed complex resistivity model. The approach was applied to data from three profiles of the Copper District of Vale do Curaca, Bahia, Brazil. The results show that it is possible to distinguish between spectral induced polarization and induction in terms of geoelectric parameters distributed in pseudosections and to identify patterns and behaviors for each of them. They constitute an important step toward mineral discrimination via analysis of analogous circuit parameters, a fundamental tool in searching metallic ores.

A coal mine in Datong is an integrated mine. At present, there is goaf in the upper and lower part of the mining coal seam. There is a lot of ponding in the goaf, which has great potential safety hazards for production. In order to find out the scope and location of ponding in goaf, the comprehensive geophysical exploration method combining transient electromagnetic method and high-density resistivity method is used to carry out the research. Firstly, the time-base, turn-off time, receiving delay, current, superposition times, and other parameters of the instrument are tested on the surface of known goaf to obtain the best instrument parameters, and the parameters are used to verify the feasibility of the research scheme; then, the transient electromagnetic method is used for large-area exploration on the surface of the mine, the suspected goaf ponding area is found through comprehensive analysis, and the high-density resistivity exploration is arranged in the suspected goaf ponding area. According to the obtained results, the scope and location of the goaf ponding area are accurately located through comprehensive analysis. The results show that there are two goaf ponding areas in the exploration area, which are located above the 8# coal seam currently mined; the range and location of goaf ponding area can be accurately obtained by using the comprehensive geophysical method of high-density electrical method and transient electromagnetic method. This method can provide reference for mine water prevention and control in Datong area and has great practical significance to ensure coal mine safety production.

The effect of grouting behind tunnel wall directly affects the surrounding ground settlement and the stability of tunnel structure, so the grouting quality detection is very necessary. As an efficient and convenient shallow geophysical exploration method, ground-penetrating radar can meet the high-resolution and non-destructive requirements of grouting quality detection behind the tunnel wall, so it is widely used in engineering in recent years. Most of the existing studies have obvious regional pertinence and special geological conditions, and there are few universal studies on the characteristics of the ground penetrating radar reflection image of the grouting defect behind the tunnel wall. In view of this, this paper uses the finite difference time domain method to simulate several grouting defects behind the wall, such as voids, water-bearing anomaly, cracks, and other grouting defects. The simulation results show that the reflection image of the direct wave is characterized by a white band with strong amplitude; the interface between primary support and second lining, primary support, and surrounding rock is also banded; the circular cavity and water anomaly characteristics are all hyperbolic, the difference is that the phase of the lower part of the radar image of the cavity anomaly is 0, and there are only hyperbolic tails on both sides, and the water-bearing anomaly also has obvious hyperbolic characteristics at each interface; the reflected wave characteristics of the rectangular crack are striped and watery and the reflected wave characteristic of rectangular cracks is striped, and the abnormal range of water-bearing cracks on the radar image is larger than that of air. The research results can provide an effective theoretical reference for the engineering application of ground penetrating radar detection of grouting defects behind the tunnel wall.

Detailed imaging of accretionary wedges reveals splay fault networks that could pose a significant tsunami hazard. However, the dynamics of multiple splay fault activation during megathrust earthquakes and the consequent effects on tsunami generation are not well understood. We use a 2‐D dynamic rupture model with complex topo‐bathymetry and six curved splay fault geometries constrained from realistic tectonic loading modeled by a geodynamic seismic cycle model with consistent initial stress and strength conditions. We find that all splay faults rupture coseismically. While the largest splay fault slips due to a complex rupture branching process from the megathrust, all other splay faults are activated either top down or bottom up by dynamic stress transfer induced by trapped seismic waves. We ascribe these differences to local non‐optimal fault orientations and variable along‐dip strength excess. Generally, rupture on splay faults is facilitated by their favorable stress orientations and low strength excess as a result of high pore‐fluid pressures. The ensuing tsunami modeled with non‐linear 1‐D shallow water equations consists of one high‐amplitude crest related to rupture on the longest splay fault and a second broader wave packet resulting from slip on the other faults. This results in two episodes of flooding and a larger run‐up distance than the single long‐wavelength (300 km) tsunami sourced by the megathrust‐only rupture. Since splay fault activation is determined by both variable stress and strength conditions and dynamic activation, considering both tectonic and earthquake processes is relevant for understanding tsunamigenesis., Plain Language Summary: In subduction zones, where one tectonic plate moves beneath another, earthquakes can occur on many different faults. Splay faults are relatively steep faults that branch off the largest fault (the megathrust) in a subduction zone. As they are steeper than the megathrust, the same amount of movement on them could result in more vertical displacement of the seafloor. Therefore, splay faults are thought to play an important role in the generation of tsunamis. Here, we use computer simulations to study if an earthquake can break multiple splay faults at once and how this affects the resulting tsunami. We find that multiple splay faults can indeed fail during a single earthquake due to the stress changes from trapped seismic waves, which promote rupture on splay faults. Rupture on splay faults results in larger seafloor displacements with smaller wavelengths, so the ensuing tsunami is bigger and results in two main flooding episodes at the coast. Our results show that it is important to consider rupture on splay faults when assessing tsunami hazard., Key Points: Multiple splay faults can be activated during a single earthquake by megathrust slip and dynamic stress transfer due to trapped waves. Splay fault activation is facilitated by their favorable orientation with respect to the local stress field and their closeness to failure. Long‐term geodynamic stresses and fault geometries affect dynamic splay fault rupture and the subsequent tsunami., Volkswagen Foundation (VolkswagenStiftung) http://dx.doi.org/10.13039/501100001663, Royal Society (The Royal Society) http://dx.doi.org/10.13039/501100000288, EC | H2020 | H2020 Priority Excellent Science | H2020 European Research Council (ERC) http://dx.doi.org/10.13039/100010663, Deutsche Forschungsgemeinschaft (DFG) http://dx.doi.org/10.13039/501100001659, National Science Foundation (NSF) http://dx.doi.org/10.13039/100000001, https://github.com/TUM-I5/SWE, https://doi.org/10.5281/zenodo.6969455

Coal mine floor limestone aquifers are a major source of water inrush from the coal seam floor and a serious threat to the safety of coal mining. In order to reduce and avoid the occurrence of water inrush within the coal mine, we use multiple detection techniques, which are geophysical exploration technology, drilling technology, water inrush accidents and tracer test, to develop a multi-faceted exploration of karst development and analyze its development characteristics in the Chaochuan mine No. 1 well. The results show that, the Cambrian limestone (CL) karst water is poor; there is a certain hydraulic connection. Near faults F5, F1, F125, and SF28, the area is less water-rich area, and the deep karst water forms a closed area; 61.54 % of shallow water inrush accidents in the Taiyuan limestone and CL karsts were caused by large tectonic and nearby shallow faults. The karst vertical zonation is shallow; the shallow water level decreased more in the West Wing of the No. 1 well than in the East Wing.

Petrophysical properties are a key element for reservoir characterization but also for interpreting the results of various geophysical exploration methods or geophysical well logs. Furthermore, petrophysical properties are commonly used to populate numerical models and are often critically governing the model results. Despite the common need for detailed petrophysical properties, data are still very scarce and often not available for the area of interest. Furthermore, both the online research for published property measurements or compilations, as well as dedicated measurement campaigns of the selected properties, which require comprehensive laboratory equipment, can be very time-consuming and costly. To date, most published research results are often focused on a limited selection of parameters only, and hence researching various petrophysical properties, needed to account for the thermal–hydraulic–mechanical behaviour of selected rock types or reservoir settings, can be very laborious. Since for deep geothermal energy in central Europe, the majority of the geothermal potential or resource is assigned to the crystalline basement, a comprehensive database of petrophysical properties comprising rock densities, porosity, rock matrix permeability, thermal properties (thermal conductivity and diffusivity, specific heat capacity) as well as rock mechanical properties as compressional and shear wave velocities, unconfined compressive strength, Young's modulus, Poisson's ratio, tensile strength and triaxial shear strength was compiled from measurements conducted at the HydroThermikum lab facilities of the Technical University of Darmstadt. Analysed samples were mostly derived from abandoned or active quarries and natural or artificial outcrops such as road cuts, riverbanks or steep hillslopes. Furthermore, samples of the cored deep wells Worms 3 (samples from 2175–2195 m), Stockstadt 33R (samples from 2245–2267 m), Weiterstadt 1 (samples from 2502–2504 m), Tiefbohrung Groß-Umstadt/Heubach, B/89–B02 and the cored shallow wells (Forschungsbohrung Messel GA 1 and 2) as well as GWM17 Zwingenberg, GWM1A Zwingenberg, Langenthal BK2/05, EWS267/1 Heubach, and archive samples of the Institut für Steinkonservierung e.V. in Mainz originating from a comprehensive large-scale sampling campaign in 2007 were investigated. The database (Weinert et al., 2020b; https://doi.org/10.25534/tudatalib-278) aims to provide easily accessible petrophysical properties of the Mid-German Crystalline Rise, measured on 224 locations in Bavaria, Hessen, Rhineland-Palatinate and Thuringia and comprising 26 951 single data points. Each data point is addressed with the respective metadata such as the sample identifier, sampling location, petrography and, if applicable, stratigraphy and sampling depth (in the case of well samples).

As a numerical method based on the Galerkin variation, the numerical manifold method (NMM) adopts a dual covering system, which is convenient for constructing high-order manifold elements and performing adaptive analysis. In this paper, the NMM is used to simulate the electromagnetic response based on the structure of the undulating terrain existing in actual geophysical exploration. The relevant system equations are derived, and a penalty function method is proposed for dealing with boundary conditions. The simulation results validate the effectiveness and accuracy of this method. Through the simulation of ground barriers and ridge models, the effect of undulating terrain on the apparent resistivity and phase is investigated, which is potentially useful for examining the complex geoelectric model characteristics as well as for terrain correction of the detection results.

Vertical Electrical Soundings (VES) afford fast and economical measurements used in geophysical exploration. VES was used for groundwater exploration at the permanent site of Waziri Umaru Federal Polytechnic, Birnin Kebbi. Eighteen (18) Vertical Electrical Sounding (Schlumberger array, maximum AB/2 distance 100 m) were performed, data were acquired using ABEM terrameter (SAS 300c), to determine the geoelectric units in the subsurface stratigraphy as well as to delineate groundwater potential in the area via electrical resistivity soundings. Field data collected was analyzed using computer software (IPI2win) which gives an automatic interpretation of the apparent resistivity in ohm-meter. Data was interpreted in terms of the resistivity and thickness of subsurface layers. Results indicates that three to five (3-5) distinct layers in the study area namely; top soil which is mainly sand, clayey sand/loose sand, sandy clay/fine sand and clay unit were delineated. The result also revealed that water bearing formation exists in the third layer in some identified VES locations i.e VES 3, VES5, VES13 and VES14 with very good aquifers, with thickness and corresponding resistivity values of 40.5, 37.5, 45.8, 60 m and 173, 148, 222 and 432 Ωm respectively. The electrical resistivity data, therefore gives reasonable accurate results that can be used to understand stratigraphy and sedimentary configuration in ground water exploration.

The gravity method is a geophysical exploration method to measure variations in the acceleration of gravity on the surface of the earth in response to variations in rocks that exist beneath the surface. In gravity exploration requires a preliminary picture as a reference for measurement. This study aims to make forward modeling synthetic OCTAVE based using synthetic data on subsurface rock structures, so as to produce intrusion and fracture models based on differences in the value of the acceleration of gravity from one point to another on the surface of the earth. Synthetic modeling with the geological parameter approach of the study area is based on variations in the price of rock density. The model parameters used in intrusion modeling are the density value of 2.7 g/cm3 and the depth of 850 meters while the fracture modeling uses a density value of 2.7 g/cm3 with a depth of 350 meters and 360 meters and a thickness of 500 meters. From intrusion modeling, the gravity vertical component of attraction force is 0.03 mGal and in the fracture modeling the gravity vertical component of attraction force is 0.0565 mGal. Based on the results of this modeling, distance curve vs. gravity anomaly response is obtained for both cases. In the intrusion rock model obtained by the profile model with an open type down. While the fracture modeling is obtained anomalous profile curve variation which states that in the fracture area with a significant change in the direction of the curve.

The relevance. Nowadays, one of the priority directions in expanding the hydrocarbon base of Russia has become the research and development of its northern regions. The Lena-Anabar oil-and-gas region is located in the North part of the Siberian platform and is characterized by a very irregular geological and geophysical exploration. Precambrian deposits are the most poorly studied, despite their quite high reservoir potential, as well as direct and indirect signs of oil and gas potential. For more effective further geological exploration work in this region, a detailed study of previously drilled well sections is necessary, with the identification of lithological features of reservoir rocks, conditions for their formation and distribution. The object: Precambrian deposits discovered by deep drilling on the territory of the Lena-Anabar oil-and-gas region. The aim of the research is to identify perspective hydrocarbon reservoirs based on the analysis of the composition, structure, sedimentary environments and reservoir properties of Precambrian sediments of the Lena-Anabar oil-and-gas region. Methods: creating sections of Precambrian deposits based on detailed macro- and microscopic analysis of core material and well logs data; correlation of sections in view of lithological, paleontological and geophysical data; genetic analysis of the main lithological types of rocks and clarification of their sedimentation conditions; estimation of the influence of sedimentation and post-sedimentation factors on formation of reservoir properties; identification of levels of potential reservoirs Results. It was established that the Precambrian section is represented by the alternation of packs of carbonate and terrigenous rocks and its accumulation took place in a large range of environments: from delta to sublittoral, with a significant prevalence of shallow-water sedimentation. It was discovered that there are potential reservoir rocks in Precambrian sediments, and the most perspective levels are related to the Vendian part of the section.

It is an honour and a pleasure to be able to review 50 years of ASEG technical material in order to choose the best. However, nominating a best paper, even with implicit disclaimers around comparis...

In the gravity method of exploration geophysics, Bouguer is the name of a specific correction to measurements, and also the name of the anomaly remaining after that correction and other corrections...

Nowadays, remote sensing technologies are playing a significant role in mineral potential mapping. To optimize the exploration approach along with a cost-effective way, narrow down the target areas for a more detailed study for mineral exploration using suitable data selection and accurate data processing approaches are crucial. To establish optimum procedures by integrating space-borne remote sensing data with other earth sciences data (e.g., airborne magnetic and electromagnetic) for exploration of Iron Oxide Copper Gold (IOCG) mineralization is the objective of this study. Further, the project focus is to test the effectiveness of Copernicus Sentinel-2 data in mineral potential mapping from the high Arctic region. Thus, Inglefield Land from northwest Greenland has been chosen as a study area to evaluate the developed approach. The altered minerals, including irons and clays, were mapped utilizing Sentinel-2 data through band ratio and principal component analysis (PCA) methods. Lineaments of the study area were extracted from Sentinel-2 data using directional filters. Self-Organizing Maps (SOM) and Support Vector Machines (SVM) were used for classification and analysing the available data. Further, various thematic maps (e.g., geological, geophysical, geochemical) were prepared from the study area. Finally, a mineral prospectively map was generated by integrating the above mentioned information using the Fuzzy Analytic Hierarchy Process (FAHP). The prepared potential map for IOCG mineralization using the above approach of Inglefield Land shows a good agreement with the previous geological field studies.

Geophysical exploration wells during the exploration of coal deposits solve many geological problems. Among them: the lithological section subdivision, allocation of coal seams, the definition of the depth of their occurrence and the angles of incidence breeds, the definition of power, structure, ash, coal quality characteristics, determination of synonymy coal seams, and others. Data of GSW used in the calculation of coal reserves in the field. Precision geophysical definition of physical and mechanical properties of rocks is estimated by comparing the results obtained with the data of GSW, and rock samples in the laboratory.Geophysical surveys of boreholes are used to solve the following geological problems: lithological dissection of the section; allocation of coal seams and determination of their depth; determining the thickness, structure and ash content of coal seams, as well as determining the characteristics of coal quality; highlighting tectonic faults in borehole sections, determining their type and amplitude; determination of hydrological operating conditions, study of the temperature and gas regime of rocks, technical condition of boreholes.In addition, GIS data is used to calculate the explored coal reserves.Interpretation of geophysical data is the clarification and explanation of the information received regarding the geology of the site and the physical and mechanical properties of the object. Interpreting geophysical data is challenging. Its solution is of great practical importance for the prospecting and exploration of mineral deposits. The article provides an overview of some of the existing methods of determining the ash content of coal on the results of GSW and forecast geological conditions of coal mining.

The lithospheric mantle structure of the Antarctic continent is of great significance of studying the polymerization and fragmentation mechanism of Gondwana and the plate movement law. Long-period magnetotelluric (LMT) is an important method to study the electrical structure of earth crust and mantle. However, been limited by the bad natural environment and logistics supply difficulties, there is no LMT record of Antarctica before. In 2018, China's 34th Antarctic scientific expedition carried out the LMT survey at the eastern edge of the Antarctic continent with a frequency range of 0.00015 Hz to 0.1 Hz. After the processing and analysis, we get three points as fellow: (1) The lithospheric mantle of Antarctica has a three-dimensional resistivity structure; (2) There are low resistivity regions in the Antarctic mantle, which may be related to thermal activity. (3) It is possible to carry out LMT measurements in eastern Antarctic and more can be done in the future.

Our ASEG President of the time, Ted Tyne, kicked off this series in February 2020 (Tyne 2020), noting that our journal Exploration Geophysics (EG) is now 50 years old – 50 years that cover three li...

The article describes the principle of operation of the device for geophysical exploration, which is based on the action of detonation waves to a limited area of the earth's surface at a shallow depth (up to 100 m), a block diagram and timing diagrams explaining the principle of the device. KEYWORDS: geophysical exploration, device, block diagram, principle of operation, timing diagram, detonation generator, phase shift, harmonic component of echo signals.

Management guru Peter Drucker is credited with the statement “you can't manage what you can't measure.” In the exploration world the most important outcome of our efforts is the discovery of new ec...

In the design and construction of structures, information on the SPT N-values and the undrained shear strength is very important for investigating problems related to stability, deformation, etc. Since the shear wave velocity (S-wave velocity) is correlated with these properties, geophysical exploration methods, such as surface wave methods, which can estimate the properties densely over a wide area, are effective for creating better geotechnical designs and building better structures. In terms of investigating the seabed using a surface wave method, the method of arranging hydrophones on the seabed and dropping a weight from a boat to generate surface waves was proposed in previous studies. The present study proposes a new method using a distinctive weight-dropping source, which causes the weight to fall vertically with little resistance from the fluid region and to generate a desirable surface wave efficiently at the impact of landing. Underwater dropping tests were carried out at two field sites to find the desirable shape for the weight-dropping source. In a fundamental field test at a tideland, the effectiveness and applicability of the proposed weight-dropping method were demonstrated through a comparison with reliable on-land survey methods using geophones. Moreover, the accuracy of the proposed method was demonstrated through a practical field test conducted at sea by comparing the SPT N-values converted from the S-wave velocity, obtained by the proposed method, with those measured by standard penetration tests. Recognizing that calm conditions are required for the waves and the currents in order to apply the proposed method, the method is expected to be an effective tool for geotechnical investigations of the seabed, and to be applicable for creating better designs and constructing better coastal and marine structures.

Reconnaissance geochemical and geophysical exploration for gold was carried out at IRI Gold field. Geological mapping was conducted and rocks, soils and sediments samples were collected. The outcome revealed rocks of the basement complex of Nigeria made up of mainly, Migmatite Gneiss, Older Granite and the Schist. The major lithology in the area is silicified sheared rocks and large quartz vein. Isolated occurrence of undifferentiated schist was found as parent material on which quartzite intruded possibly during a major geological activity. Shattering of the rocks left boulders and rubbles of quartzite all around two major ridges within the study area. The rocks have shown weak geochemical anomaly except in two locations were positive anomalies were observed and identified as target for further exploration. Gold veins are prominent in the area suggesting potential gold mineralization. Interpretation of the aeromagnetic data give the orientations of the structural features, the major structural trend in the area is NE-SW. The lineaments extracted from the magnetic data range in length from 46.43m to about 1251.66m. Most of the lineaments extracted from the area are subsurface within the quartz-mica and migmatites while some of them have surface expressions even though not clearly defined. These magnetic lineaments could be the contacts between two rock types of contrasting magnetic susceptibility or edges of structures that could be faults or intrusive bodies. Interpreted satellite data show several subsurface structures which could be hosts to gold mineralization in the area. Results of the geochemical analysis of rocks, soils and sediments were super imposed on the interpreted aeromagnetic data and similar geochemical and geophysical signatures were established. Index Terms: Gold mineralization, aeromagnetic data, geochemical data, schist belt, Nigeria

My first thought, when asked to nominate a paper for the ASEG’s 50th anniversary best of Exploration Geophysics series, was to look for a paper that represented a major milestone in geophysics in m...

Memories. While admiring the detail of pixelated perfection in some recent magnetic images, I recalled some comments I made at the Applied Magnetic Interpretation Symposium held 42 years ago at the...

In this paper, we present an open python procedure with Jupyter notebook, for data extraction and vectorization of geophysical exploration profile. Constrained by observation routes and traffic conditions, geophysical exploration profiles tend to bend curved roads for easy observation, however, it must be projected onto a straight line when data processing and analyzing. After projection, we don't know the true position of the obtained crustal structure. Nonetheless, when the results used as an initial constraint condition for other geophysical inversion, such as gravity inversion, we need to know the true position of the data rather than the distance to the starting point. We solved this problem by profile vectorization and reprojection. The method can be used for extraction data of various geophysical exploration profiles, such as seismic reflection profiles, gravity profiles. Keywords: Data extraction, Vectorization, Profile, Geophysical exploration, Python

The article presents the quantitative and qualitative characteristics of a prototype of a seismic non-explosive source with an electromagnetic drive and an assessment of the possibilities of its use during geophysical exploration for oil and gas with increased environmental requirements.

Geophysical exploration of archaeological sites has been a successful tool becoming more and more popular in the last decades. Many archaeological features can be detected with magnetic gradiometry (MGR), such as fire places, burned loam, metal artifacts, or other remnants, which produce a remanent magnetic signal detectable on the surface. However, as magnetic minerals are also present in natural settings, e.g. sedimentary and magmatic rocks and sediments derived from these host rocks, the MGR signal from archaeological artifacts is often embedded in a broader geomorphological signal, which makes separation of the different sources difficult. We provide geophysical data from two complex archaeological sites in northern Germany, which have been obtained with different methods, e.g. magnetic gradiometry (MGR), electrical resistivity tomography (ERT), electro-magnetic mapping (EM), and ground-penetrating radar (GPR). The combination of geophysical methods maps different material properties of both the geomorphological and the archaeological sources. We then use the three-dimensional modeling tool PREDICTOR to analyze the sources for the geophysical signals, e.g. the dominant signal in Leimbach, resulting from infill of palaeo-channels in the settlement area, and fire places as well as shafts in the hill fort of Lossow. The model prediction enables us to quantify the structures in the sub-surface and therefore helps to unravel complex situations often present in archaeological excavations.

Recurrent and large forest fires negatively impact ecosystem, air quality, and human health. Moderate Resolution Imaging Spectroradiometer fire product is used to identify forest fires over central India domain, an extremely fire prone region. The study finds that from 2001 to 2020, ∼70% of yearly forest fires over the region occurred during March (1,857.5 counts/month) and April (922.8 counts/month). Some years such as 2009, 2012, and 2017 show anomalously high forest fires. The role of persistent warmer temperatures and multiple climate extremes in increasing forest fire activity over central India is comprehensively investigated. Warmer period from 2006 to 2020 showed doubling and tripling of forest fire activity during forest fire (February–June; FMAMJ) and non‐fire (July–January; JASONDJ) seasons, respectively. From 2015 JASONDJ to 2018 FMAMJ, central India experienced a severe heatwave, a rare drought and an extremely strong El Niño, the combined effect of which is linked to increased forest fires. Further, the study assesses quinquennial spatiotemporal changes in forest fire characteristics such as fire count density and average fire intensity. Deciduous forests of Jagdalpur‐Gadchiroli Range and Indravati National Park in Chhattisgarh state are particularly fire prone (>61 fire counts/grid) during FMAMJ and many forest fires are of high intensity (>45 MW). Statistical associations link high near surface air temperature and low precipitation during FMAMJ to significantly high soil temperature, low soil moisture content, low evapotranspiration and low normalized difference vegetation index. This creates a significantly drier environment, conducive for high forest fire activity in the region., Key Points Compared to 2001–2005, central India domain forest fire activity during 2006–2020 doubled in forest fire season and tripled in non‐fire seasonRole of persistent warmer temperatures and multiple climate extremes in increasing forest fire activity over central India is highlightedDeciduous forests of Jagdalpur‐Gadchiroli Range and Indravati National Park are extremely fire prone and fires are of high intensity

Following extreme drought during the 2019–2020 bushfire summer, the eastern part of Australia suffered from a week‐long intense rainfall and extensive flooding in March 2021. Understanding how much water storage changes in response to these climate extremes is critical for developing timely water management strategies. To quantify prompt water storage changes associated with the 2021 March flooding, we processed the low‐latency (1–3 days), high‐precision intersatellite laser ranging measurements from GRACE Follow‐On spacecraft and determined instantaneous gravity changes along spacecraft orbital passes. Such new data processing detected an abrupt surge of water storage approaching 60–70 trillion liters (km3 of water) over a week in the region, which concurrently caused land subsidence of ∼5 mm measured by a network of ground GPS stations. This was the highest speed of ground water recharge ever recorded in the region over the last two decades. Compared to the condition in February 2020, the amount of recharged water was similar but the recharge speed was much faster in March 2021. While these two events together replenished the region up to ∼80% of the maximum storage over the last two decades, the wet antecedent condition of soils in 2021 was distinctly different from the dry conditions in 2020 and led to generating extensive runoff and flooding in 2021., Key Points New GRACE Follow‐On gravity data processing quantified prompt changes in water storage by the heavy rainfall and flooding in March 2021The eastern Australia experienced the highest speed of ground water recharge and wet antecedent soils were responsible for extensive flooding in 2021The study demonstrated the feasibility of rapid processing (1–3 days) for immediate assessment of mass changes from extreme events

We present a data‐driven approach to clustering or grouping Global Navigation Satellite System (GNSS) stations according to observed velocities, displacements or other selected characteristics. Clustering GNSS stations provides useful scientific information, and is a necessary initial step in other analysis, such as detecting aseismic transient signals (Granat et al., 2013, https://doi.org/10.1785/0220130039). Desired features of the data can be selected for clustering, including some subset of displacement or velocity components, uncertainty estimates, station location, and other relevant information. Based on those selections, the clustering procedure autonomously groups the GNSS stations according to a selected clustering method. We have implemented this approach as a Python application, allowing us to draw upon the full range of open source clustering methods available in Python's scikit‐learn package (Pedregosa et al., 2011, https://doi.org/10.5555/1953048.2078195). The application returns the stations labeled by group as a table and color coded KML file and is designed to work with the GNSS information available from GeoGateway (Donnellan et al., 2021, https://doi.org/10.1007/s12145-020-00561-7; Heflin et al., 2020, https://doi.org/10.1029/2019ea000644) but is easily extensible. We demonstrate the methodology on California and western Nevada. The results show partitions that follow faults or geologic boundaries, including for recent large earthquakes and post‐seismic motion. The San Andreas fault system is most prominent, reflecting Pacific‐North American plate boundary motion. Deformation reflected as class boundaries is distributed north and south of the central California creeping section. For most models a cluster boundary connects the southernmost San Andreas fault with the Eastern California Shear Zone (ECSZ) rather than continuing through the San Gorgonio Pass., Key Points Unsupervised clustering methods provide a data‐driven way of analyzing and partitioning Global Navigation Satellite System observations of crustal deformationDeformation is distributed across the San Andreas fault system but is localized at the creeping section in central CaliforniaThe Southern San Andreas fault connects with the Eastern California Shear Zone rather than the rest of the San Andreas fault system

Aeromagnetic exploration is an important method of geophysical exploration. We study the compensation method of the towed bird system and establish the towed bird interference model. Due to the geomagnetic gradient changing greatly, the geomagnetic gradient is considered in the towed bird interference model. In this paper, we model the geomagnetic field gradient and analyze the influence of the towed bird system on the aeromagnetic compensation results. Finally, we apply the ridge regression method to solve the problem. We verify the feasibility of this compensation method through actual flight tests and further improve the data quality of the towed bird interference.

At present time, rock mechanics is considered an important science during the phase of design and implementation of any project in Civil and Mining Engineering (highway, bridges, tunnels, dams, and so on.) especially when we speak about interaction between the project and the rock masses by choosing the appropriate foundation. In addition, rock masses slopes stability is a real problem and represents an important concern in Assyr Province in order to avoid rock fall process on the main roads and buildings. Therefore, due to the characteristics of this province, where various mountainous terrain in which various metamorphic and igneous rocks can be investigated. For this reason, it is necessary to explore, inspect, investigate and understand the natural stresses within these rock masses taking into a consideration the third dimension. Moreover, we assumed that the rock masses considered as isotropic medium in the first time. In the second phase, it considered as anisotropic medium introducing the thickness of each layer in the model. In another hand, based on literature review, several methods of measuring natural stresses in rock masses have been used, including the over-coring method with CSIRO cell involved in this research to estimate the natural stresses using 3D Finite Element modeling. In this sense, the state of stresses within the rock masses depends on the characteristics of CSIRO cell and the dimension of the over-coring hole. Furthermore, in order to achieve the 3D modeling the characteristics of the rock masses mentioned before introduced in the model using "Surfrac" program written in Pascal and FORTRAN, coupled with "Abaqus" software to simulate the stresses matrix in the model. As a result, the main findings of this research is summarized in three points: the first, dealing with the CSIRO cell itself where the direction of the gauge is important during the measurement of stresses, in fact, the perpendicular gauges work better than the parallel to the hole axis. The second one, it is evident from the model that the direction of hole must be perpendicular to the dip direction of the rock layers allows to give better results compared to others. The third one, the selection of the measurement site requires involving the regional stresses of the study area according to geological investigation. Finally, it is interesting to carry out geophysical exploration in the study area to understand the local tectonic movement of rock masses. Moreover, detailed map can be highlighted the main fractures and faults network and overlap it with the most important projects deployed in Assyr province for maintenance and monitoring.

A number of empirical correlations have been achieved between the hydraulic properties measured through geoelectrical methods and water well data of Arak Aquifer located in Markazi province, Iran. The geoelectrical method of Vertical Electrical Sounding (VES) technique was used to calculate the hydraulic properties of the aquifer. Through the VES technique, the pivotal hydraulic properties such as porosity, hydraulic conductivity, and specific yield of the layers were calculated. The results of VES technique were compared with the data obtained from seven observation water wells that were already drilled as exploratory coring boreholes in the region. The results demonstrate that as the porosity and hydraulic conductivity of the water-bearing layer increase, the results of VES technique appear much identical to the water well records. Furthermore, the specific yield was calculated as 4.6% that was very close to the value of 3.5% measured through the previous pumping tests. Moreover, VES technique predicted the water table of the aquifer very close to the water level monitored in the observation water wells. The obtained correlations can be used as an alternative for drilling of new observation wells that are inefficient in time and expense, and may encounter environmental limitations of drilling and site construction.

As one of the most important methods in geophysical exploration, seismic exploration is widely used in geological resource exploration, geological disaster early warning, and other fields. Existing seismic exploration instruments mostly use electromechanical geophones for sensing, and electromechanical geophones are point sensors. In oil and gas exploration and natural seismic monitoring, point sensors must be arrayed to ensure the continuity of the seismic wave distribution. There are problems such as difficult deployment and long-term maintenance, and its detection capacity and density are also limited by cost. Optical fiber is both a sensor and a transmission medium. A large number of sensor arrays can be realized by using optical fiber. In exploration applications, only one optical cable needs to be deployed or the existing communication optical cable is directly used, which is relatively low in difficulty and cost. Under the premise of ensuring high-level data and high-density acquisition, it can still achieve a detection length of tens of kilometers, which has important potential application value in the field of seismic exploration where exploration targets are increasingly deep and refined. The seismic prospecting instrument participated in a ground fissure state monitoring test based on an active source in a certain area. In the test, the existing buried and underground fiber optic cables were used to successfully monitor the seismic waves, and the monitoring track spacing reached 4 m; the output waveform that is consistent with the existing geophones is obtained, which shows a higher sensitivity than the existing geophones.

Orbital geophysical investigations of Enceladus are critical to understanding its energy balance. We identified key science questions for the geophysical exploration of Enceladus, answering which would support future assessment of Enceladus' astrobiological potential. Using a Bayesian framework, we explored how science requirements map to measurement requirements. We performed mission simulations to study the sensitivity of a single spacecraft and dual spacecraft configurations to static gravity and tidal Love numbers of Enceladus. We find that mapping Enceladus' gravity field, improving the accuracy of the physical libration amplitude, and measuring Enceladus' tidal response would provide critical constraints on the internal structure, and establish a framework for assessing Enceladus' long-term habitability. This kind of investigation could be carried out as part of a life search mission at little additional resource requirements., 21 pages, 6 figures. A paper submitted to PSJ, which is an extension of the white paper previously submitted to the decadal survey

The effects of peat burning on organic‐rich agricultural soils of the Mezzano Lowland (NE Italy) were evaluated on soil profiles variously affected by smoldering. Profiles were investigated for pH, electrical conductivity, bulk density, elemental and isotopic composition of distinct carbon (and nitrogen) fractions. The results suggest that the horizons affected by carbon loss lie at depths 10–70 cm, where the highest temperatures are developed. We suggest that the exothermal oxidation of methane (mediated by biological activity) plays a significant role in the triggering mechanism. In the interested soils we estimated a potential loss of Soil Organic Carbon of approximately 110 kg m −2 within the first meter, corresponding to 580 kg CO2 m −3. The released greenhouse gas is coupled with a loss of soil structure and nutrients. Moreover, the process plausibly triggers mobility of metals bound in organometallic complexes. All these consequences negatively affect the environment, the agricultural activities and possibly also health of the local people., Key Points Peat burning in the Mezzano Lowland is a process active since wetland reclamation and variously affects the soil structure and carbon contentThe main carbon loss occurs in the depth interval 10–70 cm, where temperature up to 750°C is recordedThe process induces negative effects to surrounding environment, agriculture activities and possibly also human health