Solid Rock Research Articles

Modelling the loosening of rock in the experimental rock mining method

Analytical description of the process of rock discontinuity caused by the operation of an experimental cutting head, in which a combination of cutting and loosening methods was used, is presented. Loosening of the rock fragment takes place after reaching the tensile or shear strength of the rock, what is more favourable compared to the classical mining methods. An analytical model of the stress in the crack initiation plane was developed using the models of rock loosening using the disc tools and relationships formulated in fracture mechanism. The special integral of the differential equation of the loosening line was determined by geometric integration. Numerical simulations of the chip loosening were also carried out using the model of the solid rock built using the Finite Element Method. The developed models of losing the rock continuity were used in numerical simulations of loosening the rock fragment to analyze the impact of the selected parameters of the mining technology, of the rock properties and geometrical features of the experimental cutting head, on the shape of the loosening line and its extend. Using the stand test results, the qualitative compliance of the shape of the loosening line, determined using the analytical model and the numerical model, with the geometrical features of the rock chips obtained in the laboratory, was confirmed. It was found that the proper selection of the design features of the cutting head, such as: a small angle of the loosening disc and a small angle of inclination of the head axis, cause a qualitative increase in the loosening range.

Fizzy Super-Earths: Impacts of Magma Composition on the Bulk Density and Structure of Lava Worlds

Lava worlds are a potential emerging population of Super-Earths that are on close-in orbits around their host stars, with likely partially molten mantles. To date, few studies have addressed the impact of magma on the observed properties of a planet. At ambient conditions, magma is less dense than solid rock; however, it is also more compressible with increasing pressure. Therefore, it is unclear how large-scale magma oceans affect planet observables, such as bulk density. We update ExoPlex, a thermodynamically self-consistent planet interior software, to include anhydrous, hydrous (2.2 wt% H2O), and carbonated magmas (5.2 wt% CO2). We find that Earth-like planets with magma oceans larger than ∼1.5 R ⊕ and ∼3.2 M ⊕ are modestly denser than an equivalent-mass solid planet. From our model, three classes of mantle structures emerge for magma ocean planets: (1) a mantle magma ocean, (2) a surface magma ocean, and (3) one consisting of a surface magma ocean, a solid rock layer, and a basal magma ocean. The class of planets in which a basal magma ocean is present may sequester dissolved volatiles on billion-year timescales, in which a 4 M ⊕ mass planet can trap more than 130 times the mass of water than in Earth’s present-day oceans and 1000 times the carbon in the Earth’s surface and crust.

Architectural conservation of the rock-hewn churches of Lalibela, Ethiopia: A study on preservation and socio-economic conservation

The 11 monolithic structures that makeup Ethiopia's Rock-Hewn structures in Lalibela were painstakingly cut out of solid rock in the 12th century. Currently, these churches are facing various issues of deterioration such as exposure to natural and human-caused harms. This article critically evaluates the architectural conservation initiatives made to preserve these amazing buildings, which are often recognized as some of the most astounding architectural accomplishments in history. It carefully examines the preservation techniques used, highlighting their cultural relevance and the inherent values crucial for maintaining the Lalibela rock-hewn churches. Through the socio-economical aspects, it draws attention to the lack of funding and lack of technical requirements. Also, sustainable conservation activities develop a sense of ownership and bring awareness to the value of protecting cultural heritage. The report suggests methods for strengthening capability and creating a special conservation fund. The study uses a qualitative research methodology focusing on in-depth case studies from Lalibela, other rock-cut structures, and published academic works. As a result, this research offers valuable suggestions to encourage efficient conservation techniques. Finally, these observations contribute to a greater comprehension of the challenges in preserving the world's architectural legacies by providing helpful references for analogous sites facing similar conservation challenges.

Characterizing the water–rock interactions and groundwater flow processes in the Paleozoic to Cenozoic strata aquifer systems with contrasting mineralogy at basin scale: Qingyi river, east China

This study aims to identify water–rock interaction and groundwater flow processes in aquifer systems with contrasting mineralogy at the basin scale. Investigations have been carried out using major ion geochemistry and environmental isotopes (δ2H and δ18O of water, δ13C values, 87Sr/86Sr ratios, and 14C activities) within aquifers with contrasting mineralogy in the Qingyi river basin (QRB, east China) composed of marine carbonate and continental granitic sediments with successive strata during Paleozoic, Mesozoic and Cenozoic. Analysis of 95 rain, surface and groundwater, and 12 solid rock samples found that dissolution of limestone, silicate minerals, and evapotranspiration dominated the hydrogeochemical process in the lower, upper, and middle basin, respectively. The various major ion and 87Sr/86Sr ratios of groundwater in each aquifer suggest that local lithology minerals dissolution controls the water–rock equilibria in the groundwater system. The 87Sr/86Sr ratios are correlated with both major ion geochemistry and δ13C values, constraining the process of varying proportions of silicate and carbonate minerals dissolution. Percolating water from soils carrying dissolved CO2 plays an important role in controlling the hydrogeochemical processes in the groundwater system throughout the QRB. Inter-aquifer flow has been proved by the well correlated relations between 87Sr/86Sr ratios and δ13C values or/and Sr/Na and Ca/Na ratios, as well as the irregular groundwater apparent 14C ages (1.78 to 8.52 kyr) with respect to position in the basin. Admixture ratios of 9–50% are derived from the groundwater in limestone aquifer. The rapid decrease in carbonate groundwater mixing ratio is accompanied by an increase in 87Sr/86Sr ratios, indicating that groundwater is derived Sr from silicate weathering and abundant carbon from the soils. Regional inter-aquifer flow occurs in the buried carbonate aquifers based on isotopic evidence, which could result in karstic groundwater leakage in the Wuhu cityside and should be given special attention.

Critical slowing down phenomenon for predicting the failure of solid rocks and cement mortar materials: Insight from acoustic emission multiparameters

Failure precursors with clear physicomechanical connotations are of great significance in predicting catastrophic instability in major constructions and rock engineering. Here, we conducted uniaxial compression tests on natural solid rocks and cement mortar materials and obtained their acoustic emission (AE) activity characteristics during the damage evolution to explore the feasibility of AE parameters in characterizing the failure precursory characteristics of building materials. Based on the critical slowing down theory, the curves of the variance and autocorrelation coefficient for AE multiparameters were analyzed. The results show that the sudden increase in the variance and autocorrelation coefficient of AE multiparameters can be used as primary and secondary criteria, respectively, for the identification of failure precursors. Their physicomechanical connotations were clear, characterizing the dominance of shear failure modes and the onset of accelerated fracture. The discriminability of failure precursors characterized by the critical slowing down of the AE energy rate, RA value, and RA/AF value was higher than that characterized by the critical slowing down of the cumulative AE ring count and peak frequency. Moreover, we found that the building materials with high brittleness, strength, and heterogeneity present a more significant critical slowing down phenomenon. In the view of early-warning time, the occurrence of precursory features identified by autocorrelation coefficient was earlier than the occurrence of precursory features identified by variance.

Toxicity and chemical composition of commercial road palliatives versus oil and gas produced waters

Across the United States, road palliatives are applied to roads for maintenance operations that improve road safety. In the winter, solid rock salts and brine solutions are used to reduce the accumulation of snow and ice, while in the summer, dust suppressants are used to minimize fugitive dust emissions. Many of these products are chloride-based salts that have been linked to freshwater salinization, toxicity to aquatic organisms, and damage to infrastructure. To minimize these impacts, organic products have been gaining attention, though their widespread adoption has been limited due to their higher cost. In some states, using produced water from conventionally drilled oil and gas wells (OGPWs) on roads is permitted as a cost-effective alternative to commercial products, despite its typically elevated concentrations of heavy metals, radioactivity, and organic micropollutants. In this study, 17 road palliatives used for winter and summer road maintenance were collected and their chemical composition and potential human toxicity were characterized. Results from this study demonstrated that liquid brine solutions had elevated levels of trace metals (Zn, Cu, Sr, Li) that could pose risks to human and environmental health. The radium activity of liquid calcium chloride products was comparable to the activity of OGPWs and could be a significant source of radium to the environment. The organic fractions of evaluated OGPWs and chloride-based products posed little risk to human health. However, organic-based dust suppressants regulated toxicity pathways related to xenobiotic metabolism, lipid metabolism, endocrine disruption, and oxidative stress, indicating their use could lead to environmental harm and health risks to operators handing these products and residents living near treated roads.

Detachment of inclined spheroidal particles from flat substrates

The detachment of fine particles attached to a solid substrate or rock surface significantly affects colloidal transport in porous media. The work is devoted to quantifying the detachment conditions for inclined oblate spheroids subjected to creeping viscous flow. A numerical and a laboratory study were conducted to systematically evaluate the impact of the orientation (pitch) angle towards the hydrodynamic moment, adhesive DLVO force, contact area, and critical detachment velocity. The methodology developed to produce stretched latex polystyrene particles reduces the geometric uncertainty of nonspherical fines. The geometry of the produced oblate spheroids is fully determined by the semi-major and semi-minor axes. For inclined attached particles, an explicit formula has been derived for the detaching velocity, where the detaching drag torque exceeds the attaching adhesion torque. The probabilistic distribution of the model parameters for the detachment velocity of the inclined particles attached to the plane substrate provides upscaling for fines detachment from the particle to porous media scale.

Investigation on Large-Scale Tests of Rock Fracturing by High-Voltage Electric Pulse with Voltage as a Variable

In this paper, we use an independently developed high-voltage electrical pulse (HVEP) system to implement fracturing of solid rocks. The discharge capacitance was 150 μF, and the voltage was increased from 8 to 14 kV to increase the discharge energy. The rock appears cracked at 14 kV and 150 μF. The parameters current, strain, and vibration are utilized to investigate the rock-breaking pattern of HVEP. An increase in voltage can generate a heightened destructive effect. The enhanced effects are reflected in the peaks of current, strain, and vibration. Cracks result in an acceleration of the rate of decay of the vibration curve. Also, the rate of variation of the peak strain raises. According to the spectrum analysis, HVEPs primarily generate low-frequency energy to crack rocks in the 0 to 2000 Hz range.

Modelling the relationship between oversize fragments and nature of rock mass for a sublevel caving operation

Rock fragmentation is vital in a sublevel caving operation. The oversize fragments are the most undesired fragmentation category because of their challenges; as such, they require special attention. This study carried out a field test in one of the LKAB’s iron ore mines in northern Sweden to analyse the occurrence of oversize fragments. The analysis involved correlation and regression tests and was performed for different types of rock masses. The results showed that an increase in the percentage of solid rock mass caused an increase in the percentage of oversize fragments. The other rock types, including slightly fractured, highly fractured, and rock mass with minor and major cavities, tended to have a reduced percentage of oversize fragments. The results indicate that oversize fragments can be predicted using linear regression or partial least square regression models with R2 values of 0.78 and 0.73, respectively.

Shoal Destruction at Mancil Rock, Conecuh River, Alabama

Shoal Destruction at Mancil Rock, Conecuh River, Alabama Joann Mossa (bio) Lumber was an important component of the economy of the rural southeastern US in the late 1800s and early 1900s, and rivers provided less expensive routes than rail for floating either timber rafts or loose logs to major ports on the coast. However, obstacles and insufficient river depths throughout much of the year limited the use of rivers for this purpose. Army engineers documented conditions in these rivers and received appropriations from Congress to fund crews to clear out obstacles such as snags, rafts, wood jams, and overhanging trees in rivers across the United States (Wohl 2014). The annual reports of the Chief of Engineers describe the quantity of wood removed, but limited records exist for the rock, marl, clay shoals, islands, and boulders destroyed or modified to allow river transportation. One of many sites where Army engineers proposed work was the Escambia-Conecuh river system in Florida and Alabama (Chief of Engineers 1879). The Chief of Engineers (1879) described the Conecuh River as “impassable for boats, and even the transportation of timber and saw-logs during high-water is difficult.” Regrettably, the maps that accompanied this report could not be located. This issue’s cover photograph depicts the Conecuh River at Mancil Rock (spelled “Mansell” and “Mancell” in some reports), an altered calcareous shoal in Escambia County, southern Alabama (31.136856 °N,-86.836702 °W) (Figures 1 and 2). According to Clarke et al. (1966), the lithology of Mancil Rock is dolomite, composed of ~57.54 percent calcium carbonate, ~34.31 percent magnesium carbonate, and ~4.8 percent iron oxides and aluminum. The shoal remnants in the foreground connect to the right or north bank, water flows through the destroyed middle section, and the distant portion on the left or south bank lies under the shadows (Figure 2). According to Hiram Haines, Assistant Engineer, “the rocks belonging to the Eocene division of the Tertiary formation are exposed and form obstructions in the shape of shoals and heavy bowlders (sic)” (Chief of Engineers 1879). For a full improvement at Mancil Rock (section 15, township 2, range 12), Haines recommended removing 11,300 cubic yards of loose rock and 1000 cubic yards of solid rock totaling $7,650 (Chief of Engineers 1879). For partial improvement, he advised removing 750 cubic yards of loose rock and 100 cubic yards of solid rock totaling $575 (Chief of Engineers 1879). After several years of work on the Escambia, moving upstream annually, in 1887 Army engineers sent two parties totaling eleven men to work on the Conecuh River near Mancil Rock for several months (Chief of Engineers 1888). One crew removed ~3000 [End Page 127] Click for larger view View full resolution Figure 1. Maps of the Escambia and Conecuh rivers and study area, showing A) the location of the watershed within the region, B) the topography and drainage basin of the Escambia-Conecuh with some of its major tributaries, and C) a close-up of the topography of the Conecuh River near Mancil Rock with an arrow pointing to the location of the photograph. snags and logs from the channel and 275 overhanging trees from the banks and the other worked to excavate a channel through the “Mancell Rocks” and remove all rocks visible in the channel at low water. Despite this effort, later reports suggest that the changes at Mancil Rock were incomplete. As Cavanaugh (1906) described: “Mansell rock is a rock reef extending from the right bank toward the left bank so as to almost close the entire river” and “a cut of 600’ to 1000’ should be made.” Referring to 1887 efforts: “some work has been done toward cutting through this reef, but nothing has been accomplished so far.” Soon afterward, Congress appropriated $31,000 for the Conecuh River through the River and Harbor Act of March 2, 1907, small in proportion to the annual commerce reported on the Escambia-Conecuh of $2,500,000 (Chief of Engineers 1907). That year, the Corps staged two barges, a derrick barge and one for the storage of dynamite. Next, the Corps removed 1658 and 1563 cubic yards of rock and marl (Chief...

Beneath the Surface: Identifying Subsurface Caves in "Gua Pandan" Using Integrated Electrical Profiling Method

One of the geopark tourism areas in East Lampung Regency, "Gua Pandan," has run into rock subsidence on the surface. As part of the subsidence prevention, indirect electrical methods between resistivity and chargeability profiling were applied to identify the presence of a subsurface cave in the study area. Two measurement lines were carried out with Wenner Alpha and Wenner Schlumberger arrays. Because the depth target is shallow (approximately 10 m) and to obtain a better resolution, each line has a stretch length of 70 m and 2 m electrode spacing. A line was measured over a known underground cave to produce a desired outcome, and the other was in an area with no cavities. Based on the results from each profile of resistivity and chargeability, an air-filled target has a value of over 5,000 and under 6 ms, respectively. Then, integrated processing of both methods generated a metal factor (MF) profile to view the presence and estimated shape of the cave/ cavities. The result represents that an MF value under 1.5 ms/Ωm is a cavity, and solid rock is over 1.5 ms/Ωm. Also, the MF level from both configurations delineates a similar section. However, a modest difference occurs in estimating the cavity shape geometry, for Wenner Apha and for Wenner Schlumberger. Furthermore, this study can be an initial step in safety assessment in the area.

Organic geochemical studies and origin of black hydrocarbon material (heavy oil) produced from Risha gas field (Jordon): insights into produced contaminated organic-inorganic materials during production

After several years of gas production, a black solid hydrocarbon material began to be produced along with the gas stream from the Risha gas field, in the northeastern part of Jordan. The main reason for the formation of this material is still unknown until this time, so knowing the source of this material is this study’s main goal. Organic geochemical studies for black solid material and effective source rocks (Lower Silurian shales) are used to determine the physical and organic components of the produced black solid material (heavy oil) and attempt to identify its source. The black solid material demonstrates high organic carbon (TOC = 12% by leco instrument) and a high calorific value, like those of oils, asphalts, and shale oils with moderate sulfur content. The gross composition of the black solid material sample is dominated by saturates and asphaltene but contains very low aromatic hydrocarbons reflecting the naphthenic oil type. Meanwhile, the Silurian extracts range between paraffinic and paraffinic-naphthenic organic matters. The biomarker indicators related depositional environment and carbon isotopic composition for the black solid material sample and Silurian extracts, show that they were relatively deposited in a reducing marine environment. The black material reveals lower maturity level than the Silurian extracts. Oil/source rock correlation study for the studied samples suggests strong affinity between the black material and Lower Silurian source rock in their source characteristics, suggesting that the black hydrocarbon material was expelled from the Silurian source rocks at low maturity stage as normal oil. This normal oil is subjected to secondary alteration process (evaporative fractionation) and was stored in the reservoir. It contaminated with some inorganic material that was introduced into the well as a component of a drilling mud additive or drill string lubricant or, potentially, in part, a corrosion product of wellbore tubulars, since significant iron was present in the sample.

Genesis of Fibrous Calcite in the Chang 7 Member of the Yanchang Formation, Ordos Basin

AbstractTo explore the genesis of the laminated calcite veins developed in the black shale of Chang 73 submember of the Ordos Basin, the petrology, microstructure and geochemistry of calcite veins are studied using thin sections, fluid inclusions, trace elements and isotopic geochemistry. The source, the time of formation, the mechanism of formation, and the dynamic background of the veins are discussed. The veins are mostly made up of calcite, mixed with lenticular or spindle‐shape solid wall rock inclusions. Three structures are identified in the calcite minerals: fibrous, rhombic cleavage, and wedge‐like structure. Trace elements and isotopes of carbon and oxygen confirm that the calcite veins were formed from a high density hydrothermal fluid. It is assumed that calcite veins formed prior to wall rock consolidation during the formation of the Qinling Orogenic Belt in the Middle and Late Triassic. The results show that the sedimentary sources of Chang 73 submember were influenced by hydrothermal materials besides terrigenous detritus. The fibrous calcite is different from the fibrous calcite reported in the morphology and mechanism of formation. In this way, the research complements and improves the morphology and the mechanism of formation of fibrous calcite.

RIMFAX Ground Penetrating Radar Reveals Dielectric Permittivity and Rock Density of Shallow Martian Subsurface

AbstractThe Mars 2020 Perseverance Rover is equipped with the RIMFAX ground penetrating radar instrument which has been continuously surveying the shallow subsurface during the rover's journey. Within the first 379 mission days, we identify hyperbolic patterns in the data, which are thought to be caused by objects such as buried boulders or cavities located in the upper 5 m of the subsurface. To obtain the first detailed estimates of radar wave propagation velocity, we match these scatterer‐generated patterns with theoretical traveltime hyperbolas, which take into account the refraction at the surface. We employ these estimates to derive the average dielectric permittivity and bulk rock density of the volume above the scatterer source. The parameters compare well with those obtained through orbital radar measurements and those measured by other instruments onboard the Perseverance Rover. Our findings are consistent with a subsurface dominated by solid rock and mafic material.

Geochemical characteristics of spherules from the Pivdenna kimberlite pipe, East Azov region (Ukraine): implications for their sources and origin

The composition of spherules and particles of native metals from the Pivdenna kimberlite pipe, Ukraine, was studied using the SEM/EDS method. Three varieties of spherules have been distinguished: titanium-manganese-iron-silicate (TMIS) spherules, Ca-rich silicate spherules, and magnetite-wustite-iron (MW-I) spherules. TMIS spherules are composed of homogeneous glass, some having a native iron core. Large TMIS spherules may contain a crystalline phase with needle-like armalcolite. Ca-rich silicate spherules can be subdivided into two subtypes: calcium-silicate (CS) spherules where SiO2 and CaO are the dominant constituents, and calcium-iron-silicate (CIS) spherules with significant FeO content. CS spherules may contain a core consisting of native phases (Fe, Fe-Si, and Mn-Si-Fe). Native metal particles are represented by native Cu and native Zn. The spherule varieties from the Pivdenna pipe are similar to those from other kimberlite pipes in the world. We infer that the formation of spherules occurred in gas-melt streams, separately from the kimberlites, and propose a model for the formation of the most common variety of spherules (TMIS and MW-I varieties) in the region of the core-mantle boundary (CMB). First, a melt of the Fe-Ti-Mn-Si-O system was formed in ultra-low-velocity zones (ULVZ) as a result of thermochemical reactions (reduction) between the molten core and solid oxide-silicate rocks. The melt then migrates to shallower levels, where a decrease in temperature initiates oxidation with the formation of SiO2-TiO2-FeO-MnO-Fe0 melt, i.e. parent melt of TMIS and MW-I spherules. We interpret the formation of native metals in kimberlites as a result of the decomposition of nitrides, which came from the Earth’s core via intratelluric flows

Life Cycle Assessment of River Sand and Aggregates Alternatives in Concrete.

Urbanization processes in Asia are still ongoing; thus, aggregate demand is expected to increase in following years. Even though construction and demolition waste is a source for secondary building materials in industrialized countries, it is not yet an alternative construction material source in Vietnam as the urbanization process is still ongoing. Thus, there is a need for river sand and aggregates alternatives in concrete, namely manufactured sand (m-sand) from primary solid rock materials and secondary waste materials. The focus in the present study for Vietnam was on m-sand sand as alternative for river sand, and different ashes as alternatives for cement in concrete. The investigations comprised concrete lab tests according to the formulations of concrete strength class C 25/30 in accordance with DIN EN 206, followed by a lifecycle assessment study in order to identify the environmental impact of the alternatives. In total 84 samples were investigated, consisting of 3 reference samples, 18 samples with primary substitutes, 18 samples with secondary substitutes, and 45 samples with cement substitutes. This kind of holistic investigation approach comprising material alternatives and accompanying LCA was the first study for Vietnam, and even for Asia, and represents a substantial added value for future policy development in order to cope with resource scarcity. The results show that with the exception of metamorphic rocks, all m-sands meet the requirements for quality concrete. In terms of cement replacement, the mixes showed that a higher percentage of ash reduces the compressive strength. The compressive strength values of the mixes with up to 10% coal filter ash or rice husk ash were equivalent to the C25/30 standard concrete formulation. Higher ash contents up to 30% lead to the reduction of the concrete quality. The LCA study's results highlighted the better environmental footprints across environmental impact categories in the 10% substitution material in comparison to the use of primary materials. The LCA analysis results showed that cement as a component in concrete holds the highest footprint. The use of secondary waste as alternative for cement provides significant environmental advantage.

CHARACTERIZATION OF AQUIFER STRUCTURES IN THE NORTHEAST BASEMENT ROCK OF BURKINA FASO

This characterization study of the aquifer horizons is based on the geostatistical analysis of the drilling data in order to map the intrinsic parameters of the aquifers, namely the size of the alterations and the size of the fissured fringe. The STRM data were also used to map the topographic levels. Cross-analysis of all these parameters with borehole flow rates allowed us to define a context pattern that is favorable to groundwater deposits, by identifying the influence of the size of these parameters on productivity. The application of the geophysical method (electric drag and geoelectric tomography) has made it possible to obtain a 2D vertical section of the subsoil structure based on the distribution of electrical resistivity. The alteration profile includes the alterite reservoir, the fissure reservoir located above the solid rock sometimes affected by fractures (fault). The size of these different horizons varies from one point to another, thus defining contexts that are more or less favorable for the existence of groundwater deposits. The alteration thickness (AT) mapping defined two map units: alteration thicknesses of 15m or less and those greater than 15m. Erosion would have played a large role in this distribution as there is a clear link between alteration thickness and topography. The alteration thickness (AT) unit of less than or equal to 15 m has great surface water potential. It is the area where the topography is fairly low, and the fractured edges are generally of considerable thickness. They frequently coincide with the large shallow areas drained by the major waterways.

Earthquake Hazard Analysis in Ciletuh Pelabuhan Ratu Geopark Area, West Java

Indonesia is situated between Asia and Australia, as well as the Indian and Pacific Oceans. This circumstance places Indonesia in a geologically complicated pattern, which increases the intensity of earthquakes, tsunamis, volcanoes, and landslides. UNESCO has classified Pelabuhanratu Ciletuh Geopark as a world heritage area. This has resulted in an explosion in tourist and development activity. Even though this tourism destination has the potential for high seismicity, there has been no analysis of the seismic hazard in this region. This study aims to map the earthquake hazard in the Ciletuh Pelabuhan Ratu Geopark Area. This will be important for determining vital assets' placement and development planning. This study employs remote sensing studies and geographic information systems to examine and classify earthquake-prone locations. We evaluated data from DEM, RBI, and soil-type maps. This method evaluates each earthquake hazard metric using the Analytical Hierarchy Process (AHP). The large research area has a slope between 0-300. Few locations have steep slopes. In the Districts of Cisolok, Cikakak, and portions of Pelabuhan Ratu, the characteristics of the huge hard rock are derived from the Quaternary volcanic deposits of Mount Endut. As a result, this region possesses a solid rock structure that can absorb an earthquake propagation wave. This dynamic process of geomorphological creation can also demonstrate that the region surrounding the lineage will feel the effects of a future earthquake. The results show that Ciemas, Simpenan, parts of Cisolok, and Pelabuhanratu districts are included in the moderate to high category of earthquake threats.

Interpretation of well logs and core data via Bayesian inversion

Estimating in situ petrophysical and compositional properties of rocks (e.g., porosity, mineralogy, and fluid saturation) from well logs and core measurements is critical for the evaluation of subsurface fluid resources. Traditional multimineral analysis of well logs is susceptible to abnormal borehole and geometric conditions, such as shoulder-bed effects and tool/borehole-related biases. Moreover, traditional multimineral analysis rarely includes uncertainty quantification, much less assessments of the impact of measurement noise, borehole conditions, and/or inaccurate rock-physics models (RPMs) on estimated properties. Probabilistic formation evaluation with credible-interval estimations can improve the outcome of mineral and fluid evaluations from well logs by explicitly incorporating the effects of measurement biases and a priori compositional and petrophysical constraints in the estimation. A probabilistic workflow is developed to estimate petrophysical/compositional properties from well logs and available core data. The workflow consists of two sequential steps: borehole measurements (e.g., density, resistivity, and gamma ray) are first converted into a layer-by-layer earth model, which consists of piecewise constant property values, with associated uncertainty estimations. The estimated earth model is tool/borehole independent, allowing for a common baseline to effectively compare properties among neighboring wells. Next, the estimated earth-model physical properties are used to derive petrophysical properties (e.g., volumetric concentration of fluid and solid rock constituents) via petrophysical joint inversion. In each step, Bayesian inversion is implemented with Markov chain Monte Carlo sampling in contrast to deterministic algorithms used by traditional multimineral methods. The developed method has the following advantages over traditional approaches: (1) it propagates uncertainty from well logs to petrophysical properties by assimilating measurement noise, tool/borehole-related biases, and RPM errors and (2) it enables the implementation of a priori knowledge per rock class to constrain the petrophysical estimation, effectively integrating field-specific core/regional geologic data. Examples of thinly laminated and organic shale formations successfully verify the reliability, efficiency, and accuracy of our estimation method.

Periclase deforms more slowly than bridgmanite under mantle conditions

Transport of heat from the interior of the Earth drives convection in the mantle, which involves the deformation of solid rocks over billions of years. The lower mantle of the Earth is mostly composed of iron-bearing bridgmanite MgSiO3 and approximately 25% volume periclase MgO (also with some iron). It is commonly accepted that ferropericlase is weaker than bridgmanite1. Considerable progress has been made in recent years to study assemblages representative of the lower mantle under the relevant pressure and temperature conditions2,3. However, the natural strain rates are 8 to 10 orders of magnitude lower than in the laboratory, and are still inaccessible to us. Once the deformation mechanisms of rocks and their constituent minerals have been identified, it is possible to overcome this limitation thanks to multiscale numerical modelling, and to determine rheological properties for inaccessible strain rates. In this work we use 2.5-dimensional dislocation dynamics to model the low-stress creep of MgO periclase at lower mantle pressures and temperatures. We show that periclase deforms very slowly under these conditions, in particular, much more slowly than bridgmanite deforming by pure climb creep. This is due to slow diffusion of oxygen in periclase under pressure. In the assemblage, this secondary phase hardly participates in the deformation, so that the rheology of the lower mantle is very well described by that of bridgmanite. Our results show that drastic changes in deformation mechanisms can occur as a function of the strain rate.