Topographic Lineaments Research Articles

Tectono-stratigraphic framework and evolution of the northwestern Arabian plate, Central Jordan

The northwestern Arabian plate has been long influenced by various processes, including late Precambrian crustal extension, Paleozoic rifting and ice-sheet loading/unloading, and inversion during the Late Cretaceous–Late Eocene times. It has been experiencing extension in a N-S direction since the Oligocene, N-S-trending strike-slip faulting along the Dead Sea Transform Fault accompanied by the N-S extension of its surroundings, as well as shortening from E to W since the Miocene. The primary objective of this research is to examine the tectono-stratigraphic development of the Central Jordan Region (CJR), located in the northwestern Arabian plate, by employing data from seismic surveys and well logs. The CJR hosts five significant fault systems: Feinan-Zekimat AlHasa, Salwan, Karak-Wadi Al Fayha, Dana, and Hasa faults. Despite the surface expressions of these faults highlighting the tectonic impacts during the Late Cretaceous-recent period, there is a lack of comprehensive research investigating how previous tectonics influenced their structural evolution. Seismic data and well-log integration provide a unique opportunity to fill this knowledge gap. Here we identified six major stratigraphic units: upper Precambrian, Cambrian, Ordovician, Silurian, Lower Cretaceous, and Upper Cretaceous. Using time-structure maps, we also identified several phases of fault growth, with evidence suggesting that faulting primarily occurred during the late Precambrian as part of the Najd Fault System. The reactivation of these faults can be attributed to the combined effects of the Late Ordovician ice-sheet loading and the uplift during the late Paleozoic to Early Cretaceous periods. The growth of all pre-existing faults was contemporaneous with a change in the regional stress field from the Late Cretaceous to the recent. The vertical correlation between the latest Cretaceous faulting of the CJR and the previously published topographic lineaments map suggests a tectonic control on the evolution of the surface structures.

Remote sensing and geophysical methods for delineating groundwater resources in schists hard rocks of the Adamawa Yadé Domain, Cameroon

The combination of remote sensing and geophysical techniques is a practical approach for mapping environmental hydrogeological setting and delineating groundwater zones. This paper applies an integrated approach to identify and extract the subsurface structures that act as conduits for the groundwater flow in the highly deformed area of the Adamawa region. Remote sensing data through the lineament’s extraction technique highlights topographic lineaments along which rivers flow in the area. The distribution of these lineaments according to the lineament density map indicates the degree of permeability or porosity of each region and thus the capability in terms of groundwater potential. The filtering of aeromagnetic data enables to produce a structural map showing various geophysical lineaments interpreted as the fault systems of the study area. These faults are the main conduits through which magnetized rocks of granitoid type intruded into the basement and groundwater flows to the subsurface. Local application of the vertical electrical sounding (VES) shows that the study area is highly fractured/faulted and composed of multiple lithologic units including two aquifer layers (clayey sands and fractured schists) with thickness ranging from 5 to 15 m and from 34 to 82 m, respectively. Geoelectric cross-sections reveal that the subsurface structures consist of horsts, followed by a progressive subsidence depicted by the NE-trending faults towards the southern depression and grabens bounded by NW- and NE-trending normal faults. These prominent structures (faults, fractures, and grabens) are considered as the conduits for the groundwater flow into hard rock aquifers of the study area.

Structural Evaluation for Groundwater Within the Crystalline Basement of Ilorin, Nigeria, Using Multisensory Data Techniques

Within the hard rock terrains, stream channels are suspected to be controlled by fractures and joints. In the same light, the topographic lineaments and the lineaments observed from the aeromagnetic anomalies are expected to reflect the structural trends within the complex. This study has therefore adopted multi-data sets results first on a regional scale to depict the structural fabric of Ilorin Sheet 223 and then at the chosen location of the University of Ilorin Main Campus, which is made up of the Basement Complex rocks. From the remote sensing map of Ilorin Sheet 223 structural trends have been divided into two: the NE-SW and the NW-SE structural trends. The aeromagnetic anomalies divide the rocks types into metamorphic (low-to-medium magnetic intensity) and igneous (high magnetic intensity) rocks. The resistivity data interpretation reveals the weathered basement at the University of Ilorin ranges from 5m to 20m. The radial sounding results reveal the structural trend to be NW-SE and NE-SW with the interconnection of joints. The radial sounding shows the rock type in the University of Ilorin Campus to be quartzitic, clayey and igneous as judged from the near hexagonal and elongated shapes of the polygons. The results reveal a good agreement between the trends of fractures derived from the radial vertical electrical sounding and that from the lineament maps. Areas with low bedrock resistivity, thick overburden, presence of two or more interconnected fractures, and high co-efficient of anisotropy indicate intense fracturing and thus, indicate areas of high groundwater potentiality and good water quality.

Mapping geologic structures from Gravity and Digital Elevation Models in the Ziway-Shala Lakes basin; central Main Ethiopian rift

This study attempts to delineate subsurface lineaments for the tectonically and volcanically active region of the Ziway-Shala Lakes basin, central Main Ethiopian rift. Most of the previously mapped subsurface structures in the region under consideration focus on delineating crustal structures thicknesses and Moho depths undulations. Moreover, surface structures in the same region were mapped using analysis of Digital Elevation Model image data. On the other hand, there are few studies that have targeted in mapping geologic structures lying at depth levels between the shallower and deeper subsurface. The objective of this research is thus to map the subsurface geologic structures/lineaments to an average depth of 3 km (crystalline basement layer depth) from surface using gravity data. These investigation results are validated by Digital Elevation Model extracted lineaments. Filtering techniques including derivative filters, upward-continuation and line module algorithm of PCI Geomatica are used to extract the gravity and topographic lineaments of the region. Orientation analyses of these subsurface and surface lineaments are made using line direction histogram of the QGIS software. Accordingly, the gravity subsurface lineaments mapped in this study are found to be dominantly oriented in the NNW-SSE to NW-SE and E-W direction on average. These results appear to be contrary to the NNE-SSW to NE-SW trending surface geologic structure mapped on the bases of actual field observation carried out by previous researchers and automatically extracted lineaments based on Digital Elevation Models data considered in this research. The subsurface lineaments mapped using gravity data are believed to govern groundwater dynamics within the basin and the adjacent basins in the area. These structural lineaments which are considered to be masked in the subsurface coincide with the orientation of the Mesozoic Ogaden rift as compared to the overlying surface structures which appear to coincide with the orientation of the Cenozoic Main Ethiopian rift.

Increased megathrust shear force drives topographic uplift in the Colombian coastal forearc

The subsidence/uplift patterns of forearc basins are controlled by subduction dynamics and are strongly dependent on the nature of the margin (erosive vs. accretionary). Here, we explore the role that increased megathrust shear force plays in triggering and sustaining the short wavelength topography of coastal forearc regions at erosive margins, where subsidence is supposed to prevail. The northern Colombian coastal forearc contains a ~ 1000 m-high mountain range (Baudó Range) that abruptly stands-up for ~300 km along the northwestern Pacific margin of South America, where the buoyant Nazca plate is subducting at a shallow angle. Field observations and stratigraphic data of Cretaceous to late Neogene volcanic and sedimentary rocks, suggest that the Baudó Range has been uplifting since the middle-late Miocene. The uplift seems to continue nowadays as evidenced by the irregular cliffed and bluffed coastline, steep slopes and high topographic ruggedness in one of the wettest regions on Earth, where weathering and landscape smoothing is expected to be intense. Earthquake focal mechanisms, together with regional-scale N-S-trending sinistral reverse fault structures, west-verging folding, and NW- and NE-oriented topographic lineaments, seems to be related to a trench-perpendicular mostly compressional stress regime. The residual topography along the coastal range of the northern Colombian forearc indicates under-compensation, which may suggest that the relatively thin (~20 km-thick) crust cannot support isostatically the observed topography. We propose that increased shear force along a wide seismogenic zone linked to the shallow subduction of the Nazca plate and a poorly lubricated interface, due to limited sediment dispersal into the trench, drive the ongoing topographic uplift of the region. In contrast, the smoother relief and lower elevations in the southern Pacific coast of Colombia could be explained by a deficit of shear force available to support higher topography.

Cenozoic uplift of the Fátima Basin, NE Brazil

The Fátima Basin is a small Cretaceous interior basin that was formed within the continental Borborema Province in northeastern Brazil. Its formation was related to the opening of the southern Atlantic Ocean. This study investigates the hypothesis of post-rift tectonic reactivation within this basin through an integrated set of geophysical (aeromagnetic), surface (outcrops), and subsurface (boreholes) data to model the tectono-stratigraphic framework of the basin. An analysis of several morphometric parameters, including the slope index, relief aspect, stream profiles, asymmetry factor (AF), stream-gradient index (SL), and valley floor width-to-height ratio (VF) was used to identify possible tectonic adjustments related to post-rift stress fields. The integration of geophysical and subsurface data showed that the basin possesses a half-graben geometry with the main basin axis trending NE-SW. Two families of topographic lineaments were identified: 1) NE-SW, corresponding to the main shear zones and faults of the Pre-Cambrian basement, and 2) NW-SE, representing faults and fractures in the adjacent basement and the sedimentary cover. A digital elevation model revealed that the maximum topographic elevation was 950 m, associated with deposits of the Paleozoic Tacaratu Formation located over the hinge line of the flexural margin of the basin. The AF values in the basin ranged between 25 and 76, and first- and second-order SL index anomalies were frequent, especially in the faulted border, the southeast sector, and the northeast sector. Analyses of the main river channels revealed VF values of around 1, which indicate active incisions in the river valleys. We suggest that the basin was subjected to differential uplift during the Cenozoic, which strongly affected the southeast and northeast sectors. Based on the exhumation of the Tacaratu Formation deposits, we estimate that the basin experienced approximately 500 m of uplift that influenced the erosion of Cretaceous deposits and adjacent basement rocks.

Gravity Analysis for Subsurface Characterization and Depth Estimation of Muda River Basin, Kedah, Peninsular Malaysia

Gravity survey is one of the passive geophysical techniques commonly used to delineate geological formations, especially in determining basement rock and the overlying deposit. Geologically, the study area is made up of thick quaternary alluvium deposited on top of the older basement rock. The Muda River basin constitutes, approximately, of more than 300 m of thick quaternary alluvium overlying the unknown basement rock type. Previous studies, including drilling and geo-electrical resistivity surveys, were conducted in the area but none of them managed to conclusively determine the basement rock type and depth precisely. Hence, a regional gravity survey was conducted to determine the thickness of the quaternary sediments prior to assessing the sustainability of the Muda River basin. Gravity readings were made at 347 gravity stations spaced at 3–5 km intervals using Scintrex CG-3 covering an area and a perimeter of 9000 km2 and 730 km, respectively. The gravity data were then conventionally reduced for drift, free air, latitude, Bouguer, and terrain corrections. These data were then consequently analyzed to generate Bouguer, regional and total horizontal derivative (THD) anomaly maps for qualitative and quantitative interpretations. The Bouguer gravity anomaly map shows low gravity values in the north-eastern part of the study area interpreted as representing the Main Range granitic body, while relatively higher gravity values observed in the south-western part are interpreted as representing sedimentary rocks of Semanggol and Mahang formations. Patterns observed in the THD anomaly and Euler deconvolution maps closely resembled the presence of structural features such as fault lineaments dominantly trending along NW-SE and NE-SW like the trends of topographic lineaments in the study area. Based on power spectral analysis of the gravity data, the average depth of shallow body, representing alluvium, and deep body, representing underlying rock formations, are 0.5 km and 1.2 km, respectively. The thickness of Quaternary sediment and the depth of sedimentary formation can be more precisely estimated by other geophysical techniques such as the seismic reflection survey.

Active tectonics along the Sheladiz seismogenic fault in the Western Zagros fold-thrust belt, Kurdistan, Northern Iraq

This study attempts to present a clear case of seismic activity caused by the Quaternary reactivation of a seismogenic blind basement fault in the Sheladiz area. This area is located within the Western Zagros fold-thrust belt in the Kurdistan region of northern Iraq, near the north-eastern margin of the Arabian plate. Focal mechanisms of largest earthquakes were provided by the Harvard CMT and UK ISC bulletins. The Sheladiz fault is a NE-trending, nearly vertical to steeply dipping, seismically active left-lateral (sinistral) strike-slip blind basement fault that extends for more than 80 km with focal depths of 18–24 km, and passes transversely through major fold structures. This fault probably coincides with the continuation of Late Precambrian Kutchuk-Duhok and Sinjar-Herki transverse basement faults that forms the boundary between the Sinjar-Abdul Aziz and Deir Al Zor-Erbil transversal blocks in the study area. Left-lateral (sinistral) strike-slip movements along this basement fault may be related to the anticlockwise rotation of the Arabian plate with respect to the Eurasian plate. The stress inversion results indicate a predominant of N-S (05°/003°) oriented maximum compressive stress (σ1) in the Sheladiz area. This present-day dominant direction supports the active deformation rates along the Arabia‐Eurasia collision zone. Earthquakes in Kurdistan are mainly produced by the neotectonic reactivation of many seismically active blind basement faults that locally occur close to the surface as major faults or well-defined structural and topographic lineaments. The findings of the present study may offer more clues to predict where future earthquakes are most likely to occur.

Orientation and Frequency Analysis of Topographic Lineaments in the Miringa Volcanic Zone of the Biu Plateau Region, Borno State, Nigeria

The aim of present study is to spatially analyze the topographic lineaments of tectonic origin in the Miringa Volcanic Zone located in the northwestern part of the Biu Plateau. To achieve such aim, SRTM of spatial resolution 12.5 m was utilized. The lineaments were automatically extracted by using PCI GEOMARTICA software version 10. This was followed by field work for ground thruting and to establish field relationships. ArcGis 10.5 software version was used for spatial analysis of lineaments while Rockworks version 16 was used in creating the Rossace used in lineament trend analysis and other related statistical variables associated with the lineaments of the study area. 2036 linear structures were identified in the area with a total length of 30,193.85 m. The maximum length of lineament recorded in the study area is 150 m while the minimum is 3.68 m. Field work revealed that most of the lineaments in the area developed from the weathering of contacts between successive volcanic beds in areas overlaid by the highly dissected plateaus, escarpment slopes and denudation hills. Trend analysis of lineaments of the study area indicates that the direction of lineaments tend to lie in the North-east to southwest direction (Azimuth 45°-225°) which has same direction with major drainage system and most of the volcanoes of the area. This signifies the presence of a major fissure trending in the north-east to south-west direction as the primary tectonic structure of the area. Subsequent exogenic processes exploited this structure leading to the formation of other micro-lineaments that trend along the same direction.

Simple method for estimating well yield potential through geostatistical approach in fractured crystalline rock formations

In inland Tanzania, because of the low annual rainfall and poor surface water runoff, increasing the supply of safe drinking water is a major issue. To solve the issue and to design for the drinking water supply at region of fractured zones in crystalline rocks, the simple method is applied to find the relationships between the pumping discharge of drilling wells and the field survey data in the Tabora Region, Tanzania. The field data used included results of electrical resistivity tomography (ERT) survey, electric resistivity borehole logging, the geological column (as geological information) and size of lineaments (as spatial information). A multiple correlation equation developed in this study demonstrates that the pumping discharge of a drilling well can be determined from two surface data sets: ERT survey results and lengths of topographic lineaments. This study also demonstrates that surface hydro-geophysical surveys are highly effective for exploration of groundwater resources in Tabora Region, and thus assist in locating potential drilling sites where water resources are scarce. Application of this equation enables prediction of the well yield potential in developing areas and is expected to increase the water supply in the Tabora Region, where water resource surveys are being conducted. Areas suitable for residential use, which are identified as regions on the application map where the well yield potential exceeds 5 m3hr-1, are found at the northern part of the Tabora Urban and Tabora Rural east and north from Tabora Urban. From the case study in the Tabora Region, this proposed simple method has possibilities to be able to apply for other regions in Tanzania and surrounding countries of Tanzania where are under similar conditions and environments to the Tabora Region.

Data acquisition by digitizing 2-D fracture networks and topographic lineaments in geographic information systems: further development and applications

Abstract. Understanding the impact of fracture networks on rock mass properties is an essential part of a wide range of applications in geosciences from understanding permeability of groundwater aquifers and hydrocarbon reservoirs to erodibility properties and slope stability of rock masses for geotechnical engineering. However, gathering high-quality, oriented-fracture datasets in the field can be difficult and time-consuming, for example, due to constraints on field work time or access (e.g. cliffs). Therefore, a method for obtaining accurate, quantitative fracture data from photographs is a significant benefit. In this paper we describe a method for generating a series of digital fracture traces in a geographic information system (GIS) environment, in which spatial analysis of a fracture network can be carried out. The method is not meant to replace the gathering of data in the field but to be used in conjunction with it, and it is well suited when field work time is limited or when the section cannot be accessed directly. The basis of the method is the generation of the vector dataset (shapefile) of a fracture network from a georeferenced photograph of an outcrop in a GIS environment. From that shapefile, key parameters such as fracture density and orientation can be calculated. Furthermore, in the GIS environment more complex spatial calculations and graphical plots can be carried out such as heat maps of fracture density. Advantages and limitations compared to other fracture network capture methods are discussed.

KONTROL STRUKTUR GEOLOGI PADA ALTERASI DAN MINERALISASI DI DAERAH CIBALIUNG, KABUPATEN PANDEGLANG, PROVINSI BANTEN

Cibaliung terletak di dalam Honje Igneous Complex yang merupakan kompleks vulkanik berumur Miosen yang memiliki dua urat kuarsa yang ekonomis untuk ditambang yaitu urat Cikoneng dan urat Cibitung. Keterdapatan urat kuarsa di Cibaliung ini telah ditambang dan diproduksi oleh PT Cibaliung Sumber Daya anak perusahaan PT Aneka Tambang Tbk. Pada proses produksinya urat kuarsa ini telah mencapai batas maksimal produksinya sehingga diperlukan cadangan baru. Metodologi penelitian yang dilakukan antara lain pengamatan struktur geologi dengan analisis kelurusan topografi, circular feature, analisis kelurusan sungai melalui citra Digital Elevation Model, dan pengukuran struktur breksiasi, slickenside, shear fracture dan gash fracture. Hasil interpretasi data lapangan dari 328 lokasi pengamatan dengan 8.114 data struktur geologi menunjukkan bahwa keterdapatan struktur geologi berbanding lurus dengan intensitas alterasi dan mineralisasi. Dari hasil metode analisis struktur dan pergerakan sesar yang dikorelasikan dengan data mineralisasi dan alterasi didapatkan 14 daerah prospek yakni Prospek Cikoneng-Cibitung, Prospek Cibengang, Prospek Rorah Kadal, Prospek Cikeni, Prospek Ramada, Prospek Mastar, Prospek Muara Cikeni, Prospek Cipatat, Prospek Ciburial, Prospek Cikamancing, Prospek Sompok Uara, Prospek Batulawang Utara, Prospek Cikarae-Cingenge, dan Prospek Ciparay. Dari beberapa prospek tersebut direkomendasikan untuk dilakukan ekplorasi lebih lanjut pada enam prospek, yakni Prospek Cibengang, Prospek Ramada, Prospek Cikoneng Barat, Prospek Cikamancing, Prospek Sompok Utara dan Prospek Batulawang Utara.

Evidence of Previous Faulting along the 2019 Ridgecrest, California, Earthquake Ruptures

ABSTRACTThe July 2019 Ridgecrest earthquakes in southeastern California were characterized as surprising by some, because only ∼35% of the rupture occurred on previously mapped faults. Employing more detailed inspection of pre-event high-resolution topography and imagery in combination with field observations, we document evidence of active faulting in the landscape along the entire fault system. Scarps, deflected drainages, and lineaments and contrasts in topography, vegetation, and ground color demonstrate previous slip on a dense network of orthogonal faults, consistent with patterns of ground surface rupture observed in 2019. Not all of these newly mapped fault strands ruptured in 2019. Outcrop-scale field observations additionally reveal tufa lineaments and sheared Quaternary deposits. Neotectonic features are commonly short (<2 km), discontinuous, and display en echelon patterns along both the M 6.4 and M 7.1 ruptures. These features are generally more prominent and better preserved outside the late Pleistocene lake basins. Fault expression may also be related to deformation style: scarps and topographic lineaments are more prevalent in areas where substantial vertical motion occurred in 2019. Where strike-slip displacement dominated in 2019, the faults are mainly expressed by less prominent tonal and vegetation features. Both the northeast- and northwest-trending active-fault systems are subparallel to regional bedrock fabrics that were established as early as ∼150 Ma, and may be reactivating these older structures. Overall, we estimate that 50%–70% (i.e., an additional 15%–35%) of the 2019 surface ruptures could have been recognized as active faults with detailed inspection of pre-earthquake data. Similar detailed mapping of potential neotectonic features could help improve seismic hazard analyses in other regions of eastern California and elsewhere that likely have distributed faulting or incompletely mapped faults. In areas where faults cannot be resolved as single throughgoing structures, we recommend a zone of potential faulting should be used as a hazard model input.

Geomorphic Response to Differential Uplift: River Long Profiles and Knickpoints From Guadalcanal and Makira (Solomon Islands)

Knickpoints have long been recognised as key geomorphic features that can be used to reveal the landscape evolution of a region. In particular, mobile knickpoints resulting from relative base-level fall record a landscape in the process of change and can encode information about the timing and rate of landscape response. Here, digital elevation model analysis is undertaken to; a) identify topographic lineaments related to active faulting, and b) extract geomorphic metrics and document associated knickpoints for rivers on Guadalcanal and Makira (San Cristobal) part of the Solomon Island chain. These islands have been experiencing uplift of up to 2 mm/yr since at least the mid Holocene on the upper (Pacific) plate of the San Cristobal Trench of the Solomon Island Forearc. For Guadalcanal, 23 out of 53 studied rivers exhibit slope-break knickpoints, characteristic of base-level fall, and 27 new topographic lineaments with ~E-W orientation are identified. By contrast, on Makira 14 of 41 studied rivers have slope-break knickpoints, where the rivers are steeper below the knickpoint than above. In addition, 76 new lineaments are inferred, trending NE-SW and likely to be extensional faults. For both Guadalcanal and Makira there is a good correlation between knickpoint elevation/catchment area and distance upstream from the sea, and a weak correlation between relief and knickpoint elevation. There are no clear relationships between the knickpoints and the new topographic lineaments. These data indicate that both islands are undergoing active river incision caused by regional tectonic uplift along an active subduction zone. On Makira, river steepness (ksn) scales with uplift, and K, coefficient of erosion, is in the range 1 x 10-5 – 7 x 10-6 m0.1yr-1, while K can be estimated as 1 x 10-5 – 5 x 10-8 m0.1yr-1 for Guadalcanal. Calculation of K for steady-state rivers demonstrates a rock strength control on the fluvial response and highlights the importance of lithology on river evolution. Furthermore, the distinct landscape response of the two islands supports the hypothesis that there are different arc segments present along the Solomon Arc and suggests that the Holocene uplift rates for Guadalcanal may not be representative of long-term uplift.

Landform mapping of Okinoshima island and sea bed of Munakata city

Abstract. Munakata city is compiling its city history now. Then, in March 2019, the natural environment part edition of "Umi, Yama, Kawa" is scheduled to be published. I had to do landform mapping of Okinoshima island and sea bed in this project. In this abstract, the geography of Okinoshima, the process of mapping and some of the results are described.The Sacred Island of Okinoshima and Associated Sites in the Munakata Region was registered as a World Heritage in July 2017. Okinoshima island is located about 70 km northwest of Kyushu main island. The island consists of a steep cliff and gentle slope and the area of the plain is small. It consists of shale, quartz porphyry, and talus deposit.Fig.1 shows the landscape of Okinoshima island from the south. The highest peak is Mt. Ichinotake, the rock on the left is Mikadobashira and the rock on the right is Tengu-iwa. There is a holy place, Okitsu-miya of Munakata Taisha at the foot of the island. Residents have unwritten taboos that forbid actions such as removing anything from the island, or revealing anything seen or heard there.Maps of land and sea bed were made by various kinds of geographic information by using GIS. They are ground elevation map, slope map, relief map and 3D image. Fundamental geospatial data of GSI (Geospatial Information Authority of Japan), map information related to isobaths of JHA (Japan Hydrographic Association) and airborne laser scanner data of Munakata city are used as the geographic information.Landform classification map was made by interpretation of each map and field survey. Classified landforms are crest， dissected valley，steep cliff，landslip lobe，talus cone， seaside and man-made land. Farthermore, geologic and topographic lineaments were interpreted.Fig.2 shows the 3D image of Okinoshima from the east. It can be identified that the height of Okinoshima is about 340 m above the flat sea bed. The topography between Okinoshima and Koyajima under the sea surface, is a shallow flat table in the west side and a concave area inclining to the east in the east side. The shape of the set of islands is like a horseshoe-shaped caldera.In this poster presentation, I would like to introduce that we can understand the landform and its formative process of Okinoshima where access is restricted from the analysis and reference of such maps by GIS.

Active sediment creep deformation on a deep-sea terrace in the Japan Trench

AbstractEighty-six new acoustic survey lines along and across the Japan Trench revealed active sediment creep deformation on a deep-sea terrace at water depths of 400–1200 m in an area of arcuate-shaped depressions that are probably associated with tectonic erosion. The most active region of creep is located on the top at the surface of the depression south of 38° N. The area of creep deformation is characterized by arcuate-shaped topographic lineaments with active folds and active normal faults stepping down trenchward. In contrast to the southern region, normal faults at the top of the depression north of 38° N cut a sedimentary sequence (Unit 1) that is acoustically transparent with continuous weak reflectors, and this is covered by the undeformed layered sediment sequence of Unit 2. Unit 2 corresponds to the period of rising sea level that extended from the latest Pleistocene to the early Holocene (14–6 ka). Thus, creep is ongoing at the top of the depression south of 38° N in the surface layer, whereas it stopped north of the depression between 14 and 6 ka. These observations might indicate that the active region jumped from north to south due to probably retrogressive sliding.

Investigation of the 1727 Newbury, Massachusetts, USA, earthquake using LiDAR imagery and P-wave velocity tomography

High-resolution LiDAR (light detection and ranging) images of northeastern Massachusetts and southeastern New Hampshire reveal a 10-km-long, NW-SE-oriented topographic lineament in northeastern Massachusetts that we interpret to be the surface expression of a SW-dipping thrust fault along which the 1727 Newbury, Massachusetts, earthquake occurred. The Newburyport lineament coincides with the northeast edge of a 10-kmlong, NW-SE-oriented ridge, herein named Merrimack ridge, that parallels the NW-SE-trending segment of the Merrimack River downstream from where it bends 90° to the southeast. The northwestern end of the Newburyport lineament coincides with a 1-km-long, ~7- to 15-m-high, NE-facing Newburyport scarp that is located just south of the bend in the river. The Newburyport lineament also parallels the NW-SE-oriented nodal planes of the focal mechanism that was generated for the 1999 Amesbury, Massachusetts, earthquake. A P-wave velocity tomographic model generated from a seismic-refraction profile across the Newburyport scarp shows a ~40-m-wide low-velocity zone dipping ~41° SW. Velocities along this zone decrease 15–50%, which suggests that the Newburyport lineament is associated with the surface expression of a SW-dipping brittle fault zone. The LiDAR images also revealed three other NW-SE-trending lineaments in the study area.

Major tectonic structures in northeastern Greece deduced from geophysical and seismological data

We apply lineaments analysis on the gravity and magnetic data of NE Greece, and combine seismological and geophysical data in order to delineate the major structural features. These methods are frequently used for extracting the dimensional and physical parameters of the buried structures that stimulate gravity and magnetic fields. These estimates concern the location, local depth, strike, dip and physical quantity contrast, of potential field contacts. We used results from previous studies in order to correct the Bouguer data for the gravity effect of the crust. The isostatic residual gravity anomalies, produced from the subtraction of the effect of the crust, are related to near-surface features. Noise suppression was achieved by slightly upward continuing the data by one cell size. Geologic significance of detected lineaments is confirmed by comparisons with the known geology, active tectonics and seismicity as well as with topographic lineaments

Using environmental tracers and modelling to identify natural and gas well-induced emissions of methane into streams

Development of shale gas wells sometimes results in migration of methane (CH4) from boreholes into aquifers. Identification of leakage has relied on analysis of CH4 in individual groundwater samples, usually from water wells; however, collection of point data is expensive and prone to artefacts. Methane analysis in streams is a novel way to find potential leakage of CH4 to groundwater. Here, dissolved hydrocarbons and geochemical tracers were measured in streams during base flow in watersheds with high densities of shale gas wells in Pennsylvania (PA) to identify characteristics related to leaking gas wells. Three streams with no known contamination from gas wells and one stream near a gas well previously reported to be leaking CH4 were investigated. The characteristics observed in the stream near the putatively leaking gas well that distinguish it from the streams without leaks include higher CH4 concentrations in riparian groundwater (as high as 4600 versus 206 μg/L), a relatively high gas influx to the stream channel (>70 versus <10 mg m−2 d−1), hydrocarbon isotopic signatures and radiogenic strontium consistent with Middle Devonian Marcellus Formation shale, and higher concentrations of modern atmospheric age tracers in groundwater. These tracer concentrations may indicate upward transport of hydrocarbons as a separate gas phase rather than in solution. In addition, the stream near the putatively leaking well was not located along a fault-related topographic lineament whereas streams with substantial natural thermogenic CH4 influxes tend to be aligned with potential geologic structures. The stream approach is an efficient technique to estimate watershed-scale groundwater compositions and fluxes of CH4 that reveal natural and anthropogenic sources of methane emissions.

Morphotectonic implication of the Paleoproterozoic Mid-Lithuanian Suture Zone

The Paleoproterozoic Mid-Lithuanian Suture Zone represents one of the major structures of the crystalline basement of Lithuania, separating the West Lithuanian and the East Lithuanian domains. This zone has shown persistently low tectonic activity during the Phanerozoic. The Mid-Lithuanian Suture Zone is marked by a distinct Middle Lithuanian topographic low underlain by a trough in the sub-Quaternary surface that suggests the morphotectonic nature of this depression. This is supported by high-precision geodetic levelling data that has unravelled the subsidence trend of the Middle Lithuanian trough. The zone is also distinct in its pattern of topographic lineaments. The persistence of the tectonic activity of the Mid-Lithuanian Suture Zone suggests that it represents a large-scale mechanical boundary of the Earth’s crust, resulting in increased accumulation of tectonic strain.