NE-SW Faults Research Articles

Hydrocarbon potential evaluation of Middle Benue Basin, East Central Nigeria using high resolution aeromagnetic data

Relatively cheap and non-intrusive magnetic geophysical technique has been employed to reduce the hydrocarbon exploration uncertainty in the Middle Benue Basin which straddles the northeastern and southeastern parts of Nigeria. Various derivatives and magnetic attributes extracted from the filtered, transformed and enhanced aeromagnetic data of the basin highlighted valuable information employed to appraise the hydrocarbon generating and preservation potentials of the basin, thus delineating the prospective regions where further search light of expensive and intrusive geophysical exploration tools could be focused. The trough delineated from the analyzed aeromagnetic data comprised of a massive 350 km NE-SW trending fan shaped sedimentary body bounded to the northwest and southeast by Basement Complex rocks. Active structural framework with dominant NE-SW fault systems which appeared to be the landward extension of the Chain and Charcot offshore fractures characterize the basement rocks that underlay the sediments. Sedimentary thickness of up to 3.68 km in some parts of the basin obtained from depth weighting analyses, indicate the possibility of hydrocarbon generation through the maturation of organic matter from available source rock(s). Analytic signal grids confirmed the occurrence of already documented volcanic intrusions in addition to newly delineated ones. These volcanics which are often renowned for compromising the hydrocarbon potential of a sedimentary basin are widespread in the western and southern parts the basin. Combination of adequately thick sedimentary units which overly structurally active basement rocks in regions of limited (very few/non) occurrence of volcanic intrusions delineate the north central region for further petroleum exploration prospect evaluation.

The Missing Link in the Genesis of the Lower Paleozoic Copper Deposits of the Anti-Atlas (Morocco): The Late Triassic Central Atlantic Magmatic Province Event

Copper mineralization in the Lower Paleozoic sedimentary cover of the Anti-Atlas (Morocco) is continually being revised not only to improve its mining capacity, but also to determine its origin, which remains a matter of debate. As evidenced by the various models proposed, the related research is fragmented, localized, and confusing. The origin of the Anti-Atlas Lower Paleozoic copper mineralization is shared between synergistic and epigenetic processes or a superposition of the two processes. Based on new tectono-magmatic data and a reinterpretation of the ore structural arrangement, we propose a link between the last concentration of copper deposits and the Late Triassic–Early Liassic CAMP (Central Atlantic Magmatic Province) tectono-thermal event, as evidenced by the significant concentration of copper mineralization in the three NE–SW corridors affected by extensional faults, some of which are filled with dolerite CAMP magma. The heat flow generated by the mafic dykes within these reactivated corridors causes mineralized fluids to up well into the sedimentary layers, depositing material rich in juvenile or leached copper, or even a mixture of the two. In some cases, these fluids are trapped by fracture systems that accompany passive folds initiated on normal faults. In other cases, these fluids can infiltrate bedding planes, and even karst caves, formed during carbonate exhumation. Notably, extensive NE–SW faults systematically cover the early Hercynian structures, suggesting that they belong to a post-Hercynian extensional episode. During the Late Triassic, the global fragmentation of the Pangaea supercontinent was manifested by the stretching of the continental crust at the margin of northwest Africa, with the simultaneous opening of the Central Atlantic Ocean and emplacement of CAMP magmatism. This last and often overlooked tectonothermal event must be considered in the remobilization and reconcentration of copper mineralization and other mineralization in Morocco.

Post-lacustrine evolution of a tectonically-controlled intermontane basin: Drainage network analysis of the Mercure basin, southern Italy

Topographic analysis, drainage network morphometry, river profile analysis, and spatial distribution of fluvio-lacustrine terraces have been used to reconstruct the drainage network evolution in the Mercure River basin, a large intermontane tectonic basin of the axial zone of southern Apennines. Morphotectonic evolution of the study area is mainly controlled by poly-kinematics high-angle WNW-ESE and NE-SW faults, which promoted the development of a complex landscape with relict landscapes and/or low-relief erosional surfaces that occurred in a staircase arrangement at the top of the landscapes or at higher altitudes than the basin infill. The creation of the accommodation space for the deposition of the thick basin infill was related to an important tectonic phase of block-faulting along N120°-trending normal faults, which occurred in the final part of the Lower Pleistocene. Such an evolution strongly controls the longitudinal profile forms of channels draining the northern sector of the study area, which are featured by a well-developed concave-up segment in river profiles of these channels between an upward trait with lower values of channel steepness and the trace of the master fault. River profiles in north-western and south-east sectors of the Mercure River basin exhibit clear knickpoints at altitudes comparable with those of the superimposed orders of relict landscapes related to the initial formation of the tectonic basin and the subsequent evolution of the endorheic basin, with a post-lacustrine geomorphological evolution of the drainage network that is controlled by fluvial incision occurring at rates comparable than those reconstructed by independent morphotectonic markers. The erosion of the threshold of the endorheic basin occurring during the base-level fall of the MIS 12 promoted a dramatic base-level fall of about 150 m, which corresponds to a mean incision rate of about 0.35 mm/yr. Post-lacustrine evolution of the Mercure basin strongly controls the morphometric features of the drainage network, which preserves a centripetal pattern with several planimetric anomalies such as counterflow and high-angle confluences, local-scale fluvial capture phenomena and drainage divide migrations.

Transtensional tectonics during the Gondwana breakup in northeastern Brazil: Early Cretaceous paleostress inversion in the Araripe Basin

Intraplate deformation during the Mesozoic breakup of West Gondwana predominantly occurred along major ancient lithospheric discontinuities. The Precambrian Patos Shear Zone (PASZ) is an inherited lithospheric discontinuity in the interior of northeastern Brazil which is closely linked to the evolution of the Araripe Basin. In this study, unlike previous interpretations of purely extensional tectonics, we conducted stratigraphic and structural field mapping as well as paleostress reconstruction to demonstrate the role of intraplate transtensional tectonics during the Araripe Basin evolution. Limited to the north by the PASZ and associated with sinistral reactivation, a set of normal to oblique NE–SW faults constituting a transtensional horsetail structure generated the initial basin geometry. Stratigraphic records of this rift phase comprise the Jurassic to Early Cretaceous Brejo Santo, Missão Velha, and Abaiara formations. Paleostress reconstruction showed a NE–SW/subhorizontal σ1 axis, a vertical σ2 axis, and a NW–SE/subhorizontal σ3 axis, resulting in a sinistral transtensional tectonic regime, which was mainly governed by intraplate processes that reflected the opening of the Brazilian East Margin. The subsequent Aptian post-rift early phase was characterized by NE–SW reverse faults and a succession of normal to oblique normal faults striking NW–SE to WNW–ESE. This fault arrangement generated a new NW–SE transtensional basin, which controlled the Barbalha Formation and modified and partially preserved the previous NE-SW transtensional basin. Paleostress reconstruction showed a NW–SE/subhorizontal σ1 axis and NE–SW/subhorizontal σ3 axis for strike-slip faults but NE–SW extension for normal faults. This is related to a second dextral reactivation of the PASZ following propagation of intraplate stress during the opening of the Brazilian Equatorial Margin. In summary, tectonic evolution of the Araripe Basin was strongly influenced by stress propagation from the Gondwana breakup into intraplate settings, with two distinct reactivations of the PASZ pre-existing basement structures which results in a paleostress inversion during basin evolution.

Building a Random Forest predictive modeling of mineral perspectivity and Mapping gold mineral prospects in Tam Ky - Phuoc Son, Quang Nam

Tam Ky - Phuoc Son area has great potential for gold mineral with 98 gold occurrences, but the evaluation of the entire gold-mineralization potential of the area is still very limited, while this is considered as a basis for planning, exploration, and mining. The paper uses an Artificial Intelligence model which has a name Random Forest to build predictive modeling of mineral perspectivity and to map the gold mineral prospect of the study area. 12 influencing factors are selected to build the dataset for model training and mapping gold minerals prospect, including Geology, fault systems (NE-SW faults, NW-SE faults, sub meridian faults, sub-latitude faults), Bouguer geophysical anomaly, a geochemical anomaly of silver (Ag), gold ( Au), lead (Pb), zinc (Zn), copper (Cu) and distance to the geologic boundary of complexes related to gold mineralization. The data which are generated from these factors are 12 fuzzy maps. This data combines with 98 occurrences’ locations to create a dataset that is used to train a model of mineral perspectivity using the Random Forest algorithm. After training the model is evaluated by validation. The results of the Random Forest predictive modeling of mineral prospects are well trained with an accuracy of 95.99% on the training set and 83.05 on the validation set, the performance of the model is excellent on both datasets with AUC of 0.993 and 0.95, respectively. Finally, a mineral perspectivity map is built using the trained model. The study area is divided into 3 types of areas: high, medium, and low prospects. The area of high prospect is 982.8 km2, covering 71% of the gold occurrences.

Genesis of the Halılar Metasediment-Hosted Cu-Pb (±Zn) Mineralization, NW Turkey: Evidence from Mineralogy, Alteration, and Sulfur Isotope Geochemistry

This study contributes to our understanding of the evolution of Halılar Cu-Pb (±Zn) mineralization (NW Turkey) based on mineralogical and geochemical results and sulfur isotope data. The study area represents local Cu-Pb with some Zn brecciated-stockwork vein type mineralization along the NE–SW fault gouge zone at the lower boundary of the Sakarkaya and Düztarla granitoid rocks. Two main zones, consisting of sericite–quartz–chlorite ± kaolinite ± pyrite (i.e., zone-1) and calcite–epidote–albite ± chlorite ± sericite (i.e., zone-2), were observed within the central ore mineral zone at the mining site. Different mineralization assemblages were recorded; the main ore mineral contains chalcopyrite, galena, pyrite, and sphalerite within alteration zone-1, and the oxidation/supergene mineralization includes covellite and goethite. The mass balance calculations show that the samples of zone-1 show an increase in SiO2, Fe2O3, K2O, and LOI along with Ag, As, Cu, Mo, Pb, S, Sb, and Zn, reflecting high pyritization with sericitization and silicification. On the other hand, the samples from zone-2 are rich in CaO; Na2O; P2O5; TiO2; LOI; and carbon-reflecting calcite, epidote, and albite alterations. A uniform magmatic sulfur source of Halılar sulfides is suggested by their mean δ34S value of −1.62‰. Furthermore, the primary metal source is metasediments and intrusive Düztarla granitoid magmatism. These observations suggest that the Halılar metasediment-hosted Cu-Pb (±Zn) mineralization was formed by epigenetic hydrothermal processes after sedimentation/diagenesis and metamorphism.

The dynamic evolution of the Lahendong geothermal system in North-Sulawesi, Indonesia

This study uses an integrated approach to characterize the dynamic evolution of the power-producing high-enthalpy geothermal system of Lahendong, North-Sulawesi, Indonesia. Lahendong has two primary reservoirs, the southern and the northern, which have been utilised for electricity production for more than twenty years. The main focus of this study is the characterisation of heat and mass flows in the system with respect to geological structures and permeability distribution. Also, it delineates how the geothermal system has evolved and the spatial variation of the response resulting from prolonged utilization of the reservoirs. This research implemented geological structure analysis on recent surface fault mapping and pre-existing fault studies from literature. Further, the study analysed well data comprising well pressure, enthalpy, drilling program reviews and tracer tests. Hydrochemical investigation compiled new and old surface and subsurface hydrochemical evolution in both the temporal and spatial domain. The results confirm several fault trends in the study area: NE-SW and NW-SE are the major striking directions, while E-W and N-S are less dominant. The most apparent trends are NE-SW striking strike-slip faults, NW-SE thrust faults and N-S and E-W striking normal faults. The faults compartmentalize the reservoir. A comparison of the southern and the northern reservoir shows that the southern one is more controlled by faults; both reservoirs rely on fractures as permeability provider and are controlled by shallow hydrogeology, as derived from the integrated analysis of transient well data. Geochemical analysis shows that the reservoir fluids have generally a higher eelectrical conductivity and are closer to fluid-rock equilibrium, probably due to boiling, compared to spring waters. Spring waters have generally become more acidic, which is an expected result of reservoir boiling and increased steam input to near-surface waters. The spatial distribution of changes shows a permeability evolution over time and also the role of structural permeability in response to changing reservoir conditions. Observing and recording reservoir data is highly important to understand the reservoir response to production and ensure the long-term sustainability of the system. Additionally, the data is critical for making a major difference in the reservoir management strategy.

Digital geologic map, petrography and U-Pb geochronology of the Río Santiago Shear Zone, southernmost Sierra Madre Occidental, western Mexico

The boundary between the Sierra Madre Occidental (SMO) and the Trans-Mexican Volcanic Belt (TMVB) is well exposed along the Santiago River, on the border of the states of Nayarit and Jalisco. This region includes a polydeformed belt produced by the relative motion between the Jalisco Block and the SMO, here defined as the “Rio Santiago Shear Zone” (RSSZ). In this work, we present detailed geological cartography, petrographic descriptions, and new zircon U-Pb ages that allow us to establish the stratigraphy of the region surrounding the RSSZ, providing temporal constraints to its tectonic evolution. In the mapped area, the base of the SMO stratigraphic column consists of a succession of massive andesitic lava flows intruded by felsic dikes and a felsic subvolcanic body of 27.5 and 27.2 Ma, and it is covered by a series of ignimbrites of 26.8 and 25.3 Ma. A red beds succession separates a second package of ignimbrites of ∼20-19 Ma, in turn capped by rhyolitic lava domes of 19.7 and 18.6 Ma and a rhyodacitic lava flows of 15.6 Ma, this Miocene succession is also intruded by a felsic body of 18.3 Ma west of the La Yesca dam. The SMO succession is covered by rocks belonging to the bimodal volcanism of the TMVB, emplaced between the end of the Miocene and the Pleistocene. The RSSZ developed through several deformation phases that occurred since the end of the Oligocene. The Oligocene succession of the SMO is affected by NE-SW and WNW-ESE trending lateral faults, NW-SE open folds and WNW-ESE and E-W trending reverse oblique faults. Some of the reverse oblique faults were later reactivated as normal faults. WNW-ESE trending normal faults associated with the Tepic-Zacoalco Rift affected the area south of the Santiago River during the Pliocene and Pleistocene. Normal faulting produced an accumulated vertical offset up to 700 m between the northern and southern regions of the Santiago River.

Late Miocene NE-SW strike-slip fault system of the Mexico basin, central Trans-Mexican Volcanic Belt: Origin, deformation, and reactivation

A NE-SW fault system, observed in the northeast portion of the eastern sector of the Trans-Mexican Volcanic Belt, has been active since the Pliocene-Holocene time with dip-slip kinematics. These NE-SW faults belong to the Tenochtitlan fault system that extends from the southwest coast of Mexico to the NE zone of the Mexico basin. The length of this fault system suggests a complex deformation history, which is unknown before the Pliocene. In addition, the kinematics of the NE-SW faults and the tectonic conditions are unknown before their current activity. In this study, we investigate the geometry and kinematics of the NE-SW faults in the Miocene rocks in the central part of the Mexico basin (Guadalupe Range) for to know the kinematics of these faults during the Late Miocene time. Our results suggest that the Miocene rocks record two deformation events, one event is related to crustal shortening which produced a strike-slip activity in the NE-SW faults during the Late Miocene. The second deformation event is associated with crustal extension and the activity of the NE-SW faults with dip-slip kinematics. This extensional event was active during the Pliocene-Holocene. The re-activation analysis and our observations in the Guadalupe Range suggests that the NE-SW normal faults in the Tizayuca-Chignahuapan region are the product of the re-activation of previous NE-SW strike-slip faults. The change in the kinematics of the NE-SW faults explains the complex geometry of the damage zone and the high amount of the geological fractures in the Miocene rocks of the Mexico Basin. The activity type of the NE-SW faults is probably related to the dynamic of the subduction process in the southwest of Mexico, associated with the change in the inclination (decrease) and the convergence velocity of the Cocos Plate.

Mapping the geological structures in the Ras El Ush field (Gulf of Suez, Egypt), based on seismic interpretation and 3D modeling techniques

The Ras El Ush field (Gulf of Suez, Egypt) is characterized by various complex structural features, such as evaporite deposits and faulting. Such complex geologic setting results in difficulties in terms of high-resolution seismic interpretation. The seismic energy was masked by the Pre-Miocene salt formation and attenuated by evaporite deposits in the upper Miocene, complicating the seismic interpretation process. Proper geophysical seismic imaging and interpretation of Ras El Ush field's associated structures and sedimentation can provide insights into the geological controls on hydrocarbon systems in the Gulf of Suez rift zone. This study interpreted post-stacked reflection seismic and well data comprising the check shot velocity data to obtain and investigate detailed information about the structural fault orientation and dip of Ras El Ush field. Seismic attributes were employed for improving the fault attributes by eliminating noise and residue of non-faulting events. Additionally, depth maps and 3D structural models were constructed for Rudeis, Nukhul and Matulla formations, the main geological formations within the area of interest. This study presents results from seismic attributes analyses to enhance the detection of the Clysmic fault-offsetting aggregate as well as the minor and major cross faults that passed through the Ras El Ush field. The structural model of the Rudeis, Nukhul, and Matulla formations in the Ras El Ush field exhibits distinct NW-SE to NE-SW fault systems. The models helped in defining geological discontinuities and structural traps, which would help in the development of the field and nearby similar hydrocarbon fields in the Gulf of Suez (Egypt).

Aeromagnetic investigation of crustal stability of Osi, north central Nigeri

High-resolution aeromagnetic data of Osi north central Nigeria has been processed with a view to establish the earthquake-prone fault zones in the area. The analytical signal amplitude, shaded relief total horizontal derivative, first vertical derivative and 3D Euler deconvolution maps produced from the residual magnetic intensity anomalies of the study area identified the structural features in the area. The locations and the orientations of the extracted magnetic lineaments were revealed by the structural map of the area and the associated rose diagram. The lineaments were observed to strike NE-SW, ENE-WSW, E-W, NW-SE, WNW-ESE, NNE-SSW and NNW-SSE. The upward continuation maps showed evidence of deep-lying faults while the source parameter imaging and spectral analysis revealed depth to magnetic sources ranging from 81 m to 402 m and 103 m to 460 m respectively. The predominant NE-SW and NNE-SSW trending faults in the study area depicted stress history related to Ifewara faults; which is an indication of possible impending earthquake occurrence in the area.

Identifying fault system and basement depth using aeromagnetic data beneath the Jahamah Platform, NE Sirt Basin, Libya

The Jahamah Platform is a part of a structural depression called the Sirt basin, located in the northern central part of Libya. The Jahamah Platform spans latitude 〖29.95〗^° N to 〖30.55〗^° N and longitudes 〖19.32〗^° E to 〖19.77〗^° E with an estimated area of about 2,187 km2. Libyan Petroleum Institute provided the data of aeromagnetic that was used in this study. The data was used to study the structure beneath the Jahamah Platform by using Oasis montaj software. Various filters from the software have been applied to enhance determining the fault system within the study area. An RTP filter was applied to the magnetic data to construct a reduction to the pole anomaly map. The subsurface structural elements underneath the study area were identified using Total horizontal derivative (THD), CET analysis, and Euler deconvolution. 2-D forward modelling of the area was constructed based on gravity data, and then the basement depth was estimated to range from 2.2 km to 3.1 km based on the model. Based on the interpretation of the constructed maps, the area has a number of faults that trend in NE-SW, NNW-SSE, N-S and NW-SE and faults depth ranging between 790 m to 3102 m.

Geophysical Evaluation of Central Nigeria Earth Tremor Activities using High Resolution Airborne Magnetic Data

The aim of this study is to investigate the actual causes of earth tremors in Central Nigeria using geophysical technique. Since 1933 till date (over 88 years), small to moderate magnitude earthquakes have either been observed or instrumentally recorded in Nigeria. However, the specific causes of the intra plate earthquakes in Nigeria is still not well known. In this study therefore, a high-resolution aeromagnetic data analysis was performed to evaluate the various theories proposed as the causes of tremor activity in central Nigeria with a view to ascertaining the actual causes of earthquakes in the West African country that lies on a stable crust. The total magnetic intensity data acquired from the Nigerian Geological Survey Agency (NGSA) in the Central Basement complex of Nigeria, was processed and filtered using the tilt derivative, lineament analysis, and advanced Analytic Signal- Hilbert Solution filter. To define the trends of both major and minor structure, a lineament plot was extracted and plotted. The analysis revealed a dominant NE-SW and NW-SE trending structure that is distributed throughout the study area. The regional North Atlantic Romanche fault system, which extends from the offshore (Niger Delta) into the continental crust, was mapped and is thought to extend from Gwagwalada in the study area's south, through Gwarinpa and Mpape, to Kwoi, and beyond Kafanchan.Findings from our study have indicated that, areas prone to Earth tremors are linked to the Romanche fault by numerous NE-SW and NW-SE faults that act as conduits for seismic energy that causes tremor. Using lineament density analysis, tremor active areas have been interpreted to be highly deformed; thus, seismic energy induced into the environment would result in tremors. This study demonstrates that the regional North Atlantic Romanche fault system is the primary source of seismic energy that causes the earth tremors in central Nigeria.

The effect of the Najd shear deformation on the Pan-African belt of the central Egyptian Nubian Shield: a synthesis for the post-collision tectonic events

This study concerns the structural setting of the central Egyptian-Nubian Shield (El Shalul area) utilizing field-structural, remote sensing, petrological and geochemical data. The exposed basement comprises ophiolitic-mélange, arc-related metavolcanics, metasediments, metagabbro-diorites and granitoids. The area experienced two stages of deformation, pre-Najd (∼850–630 Ma) and Najd-related (∼630–580 Ma). The pre-Najd stage is represented by the assembly of arc-terranes and their N-ward extrusion while the Najd-related stage encompasses three deformation phases. D1 is post-collision extensional event, depicting lateral spreading of tectonic terranes and NW-ejection of ophiolites. The emplacement of El Shalul granite (∼630 Ma) and deposition of molasse sediments in E-W and NW-SE extensional basins (Zeidun and Meesar) are D1- related. Following extension is a protracted phase of compression, shearing and transpression. It was commenced with NW-SE shortening (D2) and deformed the extensional basins by folding and thrusting with mild effect on the other basement units. Sinistral shearing (D3a) and transpression (D3b) along the NW-trending faults superseded the D2 compression, while dextral shearing (D3c) on the ENE-WSW and NE-SW faults overprinted the NW-SE penetrative structures and controlled the emplacement of post-granitic dykes. The significant conclusions of this study include (1) El Shalul granite complex is a large alkaline granitic sheet emplaced during a post-collision extensional regime and suffered the subsequent ∼630–580 Ma top-to-NW sinistral shearing and SW-directed thrusting (not a gneissic core complex) and (2) The NW-SE and NE-SW structural trends are not conjugated.

New constraints on tectonism and magmatism from the eastern sector of the Trans-Mexican Volcanic Belt (Chignahuapan Horst, Puebla, México)

The Quaternary Acoculco (<2.7 my) and Los Humeros (<46 ky) calderas, located in the eastern sector of the Trans-Mexican Volcanic Belt (TMVB), are separated by a regional structure known as the Chignahuapan Horst (ChH). The tectonic and magmatic evolution of the ChH comprises four stages: 1) Upper Cretaceous-Paleocene Laramide orogeny, related to the deformation of sedimentary successions; 2) a sedimentary hiatus followed by the initial stage of the TMVB (Middle Miocene); 3) a Miocene NE-SW oriented extension responsible for the NW-SE normal faults that controlled the volcanic processes and the emplacement of calc-alkaline magmas that formed the Aquixtla sequence; 4) a magmatic hiatus prolonged until 1.6 ± 0.15 my; 5) Pliocene-Quaternary normal faults controlled the emplacement of tholeiitic-transitional magmas and the monogenetic volcanism distribution that formed the Apizaco-Chignahuapan sequence.Coevally to the Miocene NE-SW and Pliocene-Quaternary NW-SE tectonic extensional phases, NE-SW and NW-SE transfer faults were developed. NE-SW normal faults and NW-SE strike-slip faults correspond to fault systems optimally oriented with the current stress field, thus, these faults can be considered as potentially active structures controlling magma emplacement and the distribution of volcanic structures at the surface.

The Seismicity of Lipari, Aeolian Islands (Italy) From One-Month Recording of the LIPARI Array

Seismic activity in volcanic settings could be the signature of processes that include magma dynamics, hydrothermal activity and geodynamics. The main goal of this study is to analyze the seismicity of Lipari Island (Southern Tyrrhenian Sea) to characterize the dynamic processes such as the interaction between pre-existing structures and hydrothermal processes affecting the Aeolian Islands. We deployed a dense seismic array of 48 autonomous 3-component nodes. For the first time, Lipari and its hydrothermal field are investigated by a seismic array recording continuously for about a month in late 2018 with a 0.1–1.5 km station spacing. We investigate the distribution and evolution of the seismicity over the full time of the experiment using self-organized maps and automatic algorithms. We show that the sea wave motion strongly influences the background seismic noise. Using an automatic template matching approach, we detect and locate a seismic swarm offshore the western coast of Lipari. This swarm, made of transient-like signals also recognized by array and polarization analyses in the time and frequency domains, is possibly associated with the activation of a NE-SW fault. We also found the occurrence of hybrid events close to the onshore Lipari hydrothermal system. These events suggest the involvement of hot hydrothermal fluids moving along pre-existing fractures. Seismological analyses of one month of data detect signals related to the regional tectonics, hydrothermal system and sea dynamics in Lipari Island.

Geophysical assessment of open dumpsite nearby Khamis Mushait industrial zone, Southwestern Saudi Arabia

Vertical electrical soundings, seismic refraction tomography, and ground magnetic measurements were taken or conducted close to an open dumpsite near Khamis Mushait, southwestern Saudi Arabia, which is characterized by shallow groundwater conditions. Structurally, intersected series of north- to northwest-trending faults affect the area. A new urban expansion and the Khamis Mushait industrial zone are close to the open dumpsite. This study evaluates the potential for leachate intrusion into groundwater aquifers. The results of electrical soundings reveal four geoelectric units: the topsoil, weathered layer, partly weathered/fractured basement, and fresh basement bedrock. At the dumpsite, relatively low resistivity values that are less than 30 Ωm characterize the topsoil, weathered layer, and partly weathered/fractured basement because of conductive leachate from the dumpsite. Besides, the results of ground magnetic data indicate that the deformation of varying intensities affects the dumpsite area, resulting in fractures developing in the N–S, NE–SW, NW–SE, and, to a lesser extent, E–W directions. Moreover, geoseismic tomographic models illustrate a low P-wave velocity zone corresponding to a low resistivity zone, and a NE–SW fault was identified from geoseismic cross-sections. Finally, these fractures and faults could become contaminant pathways for shallow aquifers around the dumpsite. To minimize the impact of such leachate, from a dumpsite, on groundwater quality and the environment in general, the dumpsite must be properly designed, constructed, and managed using engineering principles.

An Integrated Multiscale Method for the Characterisation of Active Faults in Offshore Areas. The Case of Sant’Eufemia Gulf (Offshore Calabria, Italy)

Diagnostic morphological features (e.g., rectilinear seafloor scarps) and lateral offsets of the Upper Quaternary deposits are used to infer active faults in offshore areas. Although they deform a significant seafloor region, the active faults are not necessarily capable of producing large earthquakes as they correspond to shallow structures formed in response to local stresses. We present a multiscale approach to reconstruct the structural pattern in offshore areas and distinguish between shallow, non-seismogenic, active faults, and deep blind faults, potentially associated with large seismic moment release. The approach is based on the interpretation of marine seismic reflection data and quantitative morphometric analysis of multibeam bathymetry, and tested on the Sant’Eufemia Gulf (southeastern Tyrrhenian Sea). Data highlights the occurrence of three major tectonic events since the Late Miocene. The first extensional or transtensional phase occurred during the Late Miocene. Since the Early Pliocene, a right-lateral transpressional tectonic event caused the positive inversion of deep (&amp;gt;3 km) tectonic features, and the formation of NE-SW faults in the central sector of the gulf. Also, NNE-SSW to NE-SW trending anticlines (e.g., Maida Ridge) developed in the eastern part of the area. Since the Early Pleistocene (Calabrian), shallow (&amp;lt;1.5 km) NNE-SSW oriented structures formed in a left-lateral transtensional regime. The new results integrated with previous literature indicates that the Late Miocene to Recent transpressional/transtensional structures developed in an ∼E-W oriented main displacement zone that extends from the Sant’Eufemia Gulf to the Squillace Basin (Ionian offshore), and likely represents the upper plate response to a tear fault of the lower plate. The quantitative morphometric analysis of the study area and the bathymetric analysis of the Angitola Canyon indicate that NNE-SSW to NE-SW trending anticlines were negatively reactivated during the last tectonic phase. We also suggest that the deep structure below the Maida Ridge may correspond to the seismogenic source of the large magnitude earthquake that struck the western Calabrian region in 1905. The multiscale approach contributes to understanding the tectonic imprint of active faults from different hierarchical orders and the geometry of seismogenic faults developed in a lithospheric strike-slip zone orthogonal to the Calabrian Arc.

Using multispectral and radar remote sensing data for geological investigation, Qena-Safaga Shear Zone, Eastern Desert, Egypt

In the present study, Qena-Safaga Shear Zone (QSSZ) has been the subject matter of detailed remote sensing investigation using Landsat-8, ASTER, and SRTM DEM data. Gathering information from these sensors allowed revealing the different lithological, geological, and structural features. Field observations were carried out to verify the remotely sensed data analysis and interpretation. A fused Landsat-8 OLI and ALOS/PALSAR data clearly improved the view of structural elements that are difficult to be revealed by optical images. The results showed that the area is controlled by the dextral ENE-WSW shearing trend which extends across the Nile at Qena Bend. Lineament analysis and lineament density map demonstrated that the area was subjected to different phases of stress; accordingly, conjugate faults were formed; most of these trends were rejuvenated. The ENE- WSW, NE-SW, and NW-SE are the major tectonic trends affecting the area but the N-S direction is less dominant. WNW, NW, NE, E, and N directions are indicated by sinistral strike-slip movements. The ENE, NE, and WNW are governed by right-lateral strike-slip movements and most of these trends controlled the emplacement of granitoids. The image transformation technique also allowed revealing hydrothermal alteration effects related to the NW-SE and NE-SW fault systems. Overall, combining of multispectral and radar data and field observations is significant for characterizing the geological features in arid regions.

Structure and kinematics of active faulting in the Hope-Kelly and Alpine Fault intersection zone, South Island, New Zealand

Using lidar, photogrammetry and field studies, we investigate the structure and kinematics of the Hope, Kelly, and Alpine faults where they converge and intersect along the Australian-Pacific plate boundary in New Zealand. Approximately 50% of the reverse-dextral slip rate of the Alpine fault in the west transfers to the dextral central Hope Fault in the east via a horsetail splay zone of distributed oblique dextral-normal shear forming the Hope-Kelly fault system. The westernmost portion of the Hope fault is misoriented for dextral slip and is likely an extensional fault that accommodates the Alpine fault slip rate change across the intersection zone. As it transitions to an extensional fault, most of the strike-slip of the Hope fault is transferred southward onto Kelly fault strands via incipient, linking fault domains of coeval NE-SW and EW-striking dextral faults. The transition from the narrow zone defining the central Hope Fault to dispersed horsetail splays of the Hope-Kelly fault system is located immediately above the eastward down-dip projection of the Alpine Fault at the base of the seismogenic zone. This suggests that structural interactions among these faults within seismogenic depths control surface rupture geometries and kinematics. Coeval intermingling of surface rupture traces transecting latest Pleistocene to Holocene landforms indicates ongoing structural interactions in active faulting at the intersection of the Hope-Kelly fault splays with the Alpine fault. The transition from dextral to dextral normal kinematics on the horsetail splay accommodates differential orogenic growth through geometrically and kinematically efficient faulting that allows extension of the Alpine fault hanging wall parallel to strike, enabling the slip rate change between the central and northern Alpine fault sections.