Uzbekistan possesses substantial yet largely underutilized geothermal resources, with an estimated geothermal potential that exceeds its hydrocarbon resources. However, geothermal exploration in this country remains limited due to the data scarcity of detailed subsurface data and the high cost of conventional exploration methods. This study presents a regional-scale geothermal prospectivity assessment in the Fergana Valley using remote sensing and Geographic Information System (GIS)-based techniques. A lineament density map derived from Shuttle Radar Topography Mission (SRTM) and land surface temperature (LST) anomalies extracted from Landsat 8 were integrated using fuzzy logic to identify areas favorable for geothermal exploration. The resulting prospectivity map was further constrained by the distribution of granitic rocks to delineate geothermal exploration target zones. Results indicate that zones of high lineament density and elevated LST anomalies are primarily concentrated within the Chatkal Range, particularly in the southeastern part, where a total of eleven geothermal exploration target zones were identified. The prospectivity model was evaluated using a prediction rate curve (PRC). The area under the curve (AUC) value of 0.74 indicates acceptable predictive performance and a reasonable level of agreement between the prospectivity model and the observed heat flow. These findings demonstrate that the integration of lineament density, LST anomalies and lithological information provides a transparent, low-cost, and transferable workflow built on openly available data for geothermal prospectivity assessment in data-limited areas, particularly in the intramontane regions of Central Asia.
We analyze more than seven years of continuous ambient seismic noise recorded at the Tres Vírgenes geothermal field (Mexico) to investigate temporal changes in reservoir-scale seismic response using horizontal-to-vertical spectral ratios (HVSR). Daily H/V amplitudes were evaluated at representative frequencies for seven stations with the highest temporal continuity and compared quantitatively with water-injection rates and local seismicity. Network-scale correlations were weak and did not remain robust after accounting for temporal dependence, while objectively defined external perturbations did not, as a group, produce immediate H/V changes larger than those observed during matched non-event periods. Nevertheless, individual episodes exhibited coherent immediate or delayed responses, indicating substantial temporal and spatial heterogeneity across the field. To investigate the physical origin of selected spectral changes, H/V curves from August 2010 and January 2013 at station TV01 were inverted using a geologically constrained one-dimensional model. The preferred model families indicate approximately 21% lower S-wave velocity in the fractured granodioritic unit and approximately 5% lower S-wave velocity in the overlying sandstone unit for January 2013 relative to August 2010, although the inversion remains inherently non-unique. Frequency-dependent sensitivity kernels show that the low-frequency mode near 0.08 Hz is primarily sensitive to deeper crystalline portions of the model, whereas sensitivity progressively shifts toward intermediate and shallow units at higher frequencies. These results show that long-term HVSR monitoring may provide complementary information on temporal changes in fractured geothermal systems when interpreted together with independent operational, seismicity, geological, and geophysical constraints, but the response is episodic, spatially variable, and should not be interpreted as a deterministic proxy for injection, seismicity, or reservoir stress or as a stand-alone operational diagnostic.
In deep rock engineering, temperature is an important factor affecting the strength of rock, which can cause the internal thermal effect of rock, lead to structural strengthening or deterioration, and then produce thermal strengthening / deterioration of strength. In order to achieve rapid and accurate prediction of granite strength after high temperature, this paper uses BPNN, Random Forest, XGBoost, LightGBM, AdaBoost-CART, SVR and KNN seven machine learning models as candidate base learners to construct Stacking integrated prediction model, in order to improve the accuracy and stability of granite strength prediction after high temperature. The results show that the machine learning method can describe the nonlinear relationship between the strength of granite after high temperature and multiple factors. The BPNN+XGBoost+AdaBoost-CART combination has the highest integral R2(0.9558), which is better than the single base learner. The RMSE, MAE and MAPE of the ensemble model are 21.628 MPa, 14.307 MPa and 8.781%, respectively, and the R2 on independent external data is 0.8823, which further reflects its external generalization ability. Kernel SHAP analysis shows that when the Stacking model predicts strength, different strength levels will be distinguished according to the mechanical boundary and loading conditions, and further combined with the heat treatment process and rock state information for correction. In addition, the supporting GUI tools provide a convenient operation interface for strength prediction and result visualization. The research results can provide data-driven methods and application references for the strength evaluation of granite after high temperature and related deep rock engineering analysis.
The 2011 Fukushima Hamadori earthquake (MJMA 7.0) triggered widespread groundwater discharge and groundwater-level changes in the Joban area, northeastern Japan. Geochemical studies have suggested that thermal groundwater in the Joban area contains contributions from deep-seated fluids possibly related to subduction processes. However, the subsurface structures that may facilitate fluid migration between deep crustal levels and shallow groundwater systems remain poorly understood. To investigate the structural framework potentially relevant to fluid migration, we integrated microseismic monitoring, microtremor surveys, gravity surveys, and magnetotelluric (MT) surveys in the southern part of Iwaki City, where groundwater discharge has continued for more than a decade after the earthquake. Microtremor and gravity surveys consistently revealed basement geometry and fault-related structural discontinuities, defining a complex fault system that segments the shallow basement. MT imaging revealed low-resistivity structures extending from depths of approximately 10 km toward shallower levels beneath and around major faults. Recent microseismicity was detected mainly at depths of 2 – 6 km, with a few deeper events overlapping part of the region where the 2011 seismic swarm occurred. Regional seismic tomography showed relatively high Vp/Vs ratios in the broader region containing the recent hypocenters. The spatial relationships among fault-related structures, low-resistivity structures, and seismicity are consistent with a possible structural relationship between deep crustal processes and the shallow thermal-groundwater system associated with the persistent surface discharge after the 2011 Fukushima Hamadori earthquake.
The resources of sedimentary basins have been and remain primary targets for exploitation. The occurrence of resources depends on processes and forcings that constrain the thermal regime of basins. Thermal anomalies provide clues to these processes and forcings. The Paris Basin is an interesting area of study in Western Europe. Its history of exploitation for centuries provides a rich source of data, such as geological, hydrogeological and thermal data (temperature profiles, DST (Drill Stem Test), BHT (Bottom Hole Temperature), etc.). We also draw on a diverse body of research spanning several decades. This study reexamines these data, which were obtained using the tools and concepts available at the time. A systematic approach is adopted, considering the basin in its entirety. The anomalies are thus viewed in their context and considered against the models and thermal processes proposed to date.This study highlights the importance of equilibrium temperature profiles which show that the current thermal regime is transient because, for instance, of paleoclimatic forcing. On the basin scale, the thermal regime is affected by advection, with topography-driven flows and also probably convection-driven flows. Moreover, flows via discreet seal bypass systems through formations that are usually described as confining produce pronounced thermal anomalies; this has rarely been observed in the onshore domain. Such seal bypass systems are found in the Paris region where water and geothermal resources are exploited intensively. These anthropic forcings result in perturbations and a transient regime. Flows through faults are also associated with pronounced thermal anomalies of several tens of degrees Celsius. Lastly, recommendations are proposed and orientations for scientific research and sustainable resource management are deduced to assist public agencies after 55 years of experience of geothermal exploitation.
