Fault Branch Research Articles

The 2017 Jiuzhaigou Earthquake: A Complicated Event Occurred in a Young Fault System

AbstractThe Minshan Uplift Zone (MUZ) is located at the eastern margin of the Tibetan Plateau, which is the junction of three tectonic terranes. The observed discrepancy between a high uplifting and low shortening rate over the MUZ is attributed to the intrusion of a viscous lower crust. In the last 50 years, several significant earthquakes occurred at the boundaries of the MUZ, that is, the Huya and Mingjiang faults. On 8 August 2017, the Jiuzhaigou earthquake (Mw 6.5) occurred on the northern extension of the Huya fault. We adopt a joint inversion of the interferometric synthetic aperture radar and teleseismic body wave data to investigate the rupture process of this event. The obtained slip model is dominated by left‐lateral strike slips on a subvertical fault presenting significant shallow slip deficit. The rupture initiation is composed of both thrust and strike‐slip mechanisms producing a non‐double‐couple solution. We also resolve a secondary fault branch forming an obtuse angle with the main fault plane at its northern end. These phenomena indicate that the northern Huya fault is a young (less mature) fault system. Focal mechanisms of the regional earthquakes demonstrate that the northern and southern Huya faults present different combinations of strike‐slip and reversed motion. We attribute such discrepancy to the lateral extension of the viscous lower crust, which appears to extrude to the east beyond the northern Huya fault, in comparison with that confined under the MUZ near the southern Huya fault. This conceptual model is also supported by geomorphological and magnetotelluric observations.

Characteristics and formation mechanisms of silicified carbonate reservoirs in well SN4 of the Tarim Basin

High-yield natural gas was discovered in well SN4 in the Ordovician Yingshan Formation in the Tarim Basin. The gas is found in unusual, silicified, carbonate reservoirs. According to the degree of silicification, the silicified reservoirs can be divided into a lower section of silicified carbonates, a middle section of limestone, and an upper section of silicified carbonates. The silicified carbonates are mainly composed of quartz and calcite, in which the reservoir space mostly occurs as vugs, inter-crystalline pores of quartz, and partial fractures. Porosity varies widely, ranging from 3 to 20.5% with strong heterogeneity. The homogenization temperatures of fluid inclusions in quartz and calcite show that the silicification temperatures were 150–190°C, with characteristics of high temperature/low salinity and low temperature/high salinity. The 87Sr/86Sr ratios of secondary calcite are 0.709336–0.709732, which are significantly higher than that of concurrent seawater, indicating that the hydrothermal fluid originated from the deep clastic strata or the basement (sialic rock). The δ13C values of the secondary calcite are similar to that of the surrounding limestone, indicating that the carbon in the secondary calcite is derived from the limestone strata, and that the secondary calcite is the product of dissolution and re-precipitation resulting from interaction between the silica-bearing hydrothermal fluids and surrounding limestones. The silicification of silica-bearing hydrothermal fluid was significantly controlled by strike-slip faults. The fluids ascending along the fault zone and branch faults interacted with the surrounding limestone in the Yingshan Formation. As a result, a large amount of quartz and secondary calcite were formed together with various types of secondary pores, resulting in excellent reservoirs.

Structural patterns of fault damage zones in carbonate rocks and their influences on petroleum accumulation in Tazhong Paleo-uplift, Tarim Basin, NW China

Abstract Based on the outcrop survey, 3D seismic data interpretation, drilling data analysis, the structural patterns and distribution of fault damage zones in carbonate strata of Tazhong Paleo-uplift were established to reveal the oil and gas enrichment law in the fault damage zones. The following findings were reached: (1) Through the filed survey, the fault damage zone system consists of fault core, damage zone with branch fault and fracture network. Affected by the active nature of the major faults, the fault damage zones differ in planar pattern and scale along the major faults. (2) 3D seismic profiles reveal that there are three types of fault damage zones in carbonate strata in Tazhong paleo-uplift, strike-slip fault damage zones, thrust fault damage zones and superimposed fault damage zones. Featuring 3 flowers and 3 root belts in vertical, the strike-slip fault damage zone can be subdivided into linear type, oblique type, feather type and horsetail type in plane. Thrust fault damage zones can be further divided into fault anticline type, anticline type and slope type. As the superimposition result of the above two kinds of fault damage zones, superimposed fault damage zones appear in three patterns, intersect type, encompassment type and penetrating type. (3) Cores from wells and geochemical data show oil and gas may migrate along the major fault and laterally. The feather type in strike-slip fault system, fault anticline type in thrust fault damage zone and intersect type in superimposed fault damage zone are possible sites for high production and efficiency wells.

Mechanics of plio-quaternary faulting around the Karliova triple junction: implications for the deformation of Eastern part of the Anatolian Scholle

ABSTRACTThe intersection of the Eurasian and Arabian plates and the smaller Anatolian Scholle created the Karlıova Triple Junction (KTJ) in eastern Turkey. In this study, we present analogue model experiments for this region and compare the results with our field observations and data from remote sensing imagery. Our comparison suggests that the sense of slip along curvilinear faults at the west of the KTJ changes along strike moving away from the principal displacement zones, from strike-slip to oblique normal and then to pure normal slip. Although, the active Prandtl cell model has been proposed to explain the overall regional fault pattern at eastern part of the Anatolian Scholle, the map view orientation of the secondary faults within the Karlıova wedge and performed analogue modelling results suggest that the passive wedge-shaped Prandtl cell model with a normal dip-slip component along slip lines is more appropriate in order to explain not only deformation pattern around the KTJ but also internal deformation of eastern part of the Anatolia. Moreover, these faults accumulate the significant amount of deformation that causes to the irregular earthquake behavior and the relatively lower geologic slip-rates along the main fault branch of boundary faults around the KTJ.Abbreviations: Strike-slip; Karlıova Triple Junction (KTJ); continental deformation; North Anatolian Fault Zone (NAFZ); East Anatolian Fault Zone (EAFZ);Varto Fault Zone (VFZ)

Analytical Study on the Reliability of Redundancy Architecture for Flight Control Computer Based on Homogeneous Markov Process

In order to analyze the reliability of redundancy architecture for flight control computer, this paper gives the analytical study on the reliability based on the Homogeneous Markov Process in “Triplex Channels & Single Module” and “Double Channels & Double Modules.” The paper analyzes the effect of fault rate and fault coverage rate on system reliabilities and MTTFs (mean time to failures). The index of fault tolerant capability is proposed. The analyzing results show that, for different redundancy architectures, the fault coverage rate or the branch fault rate have different effects on the reliability. Especially, the influence of the branch fault rate is more significant. In addition, the fault tolerant capability of the redundant system to multiple faults is determined by the system architecture scheme and the fault coverage rate. The results show that the method proposed in this paper can analyze reliability of redundancy architecture effectively.

Postobductional extension along and within the Frontal Range of the Eastern Oman Mountains

The Oman Mountains formed by late Cretaceous obduction of the Tethys-derived Semail Ophiolite. This study concerns the postobductional extension on the northern flank of the mountain belt. Nine sites at the northern margins of the Jabal Akhdar/Nakhl and Saih Hatat domes of the Eastern Oman (“Hajar”) Mountains were investigated. The northern margins are marked by a system of major interconnected extensional faults, the “Frontal Range Fault”. While the vertical displacements along the Saih Hatat and westerly located Jabal Nakhl domes measure 2.25–6.25 km, 0.5–4.5 km and 4–7 km, respectively, it amounts to 1–5 km along the Jabal Akhdar Dome. Extension had started during the late Cretaceous, towards the end of ophiolite emplacement. Two stages of extension can be ascertained (late Cretaceous to early Eocene and probably Oligocene) at the eastern part of the Frontal Range Fault System (Wadi Kabir and Fanja Graben faults of similar strike). Along the intervening and differently striking fault segments at Sad and Sunub the same two stages of deformation are deduced. The first stage is characterized again by extension. The second stage is marked by dextral motion, including local transtension. Probable Oligocene extension affected the Batinah Coast Fault while it also affected the Wadi Kabir Fault and the Fanja Graben. It is unclear whether the western portion of the Frontal Range Fault also went through two stages of deformation. Bedding-parallel ductile and brittle deformation is a common phenomenon. Hot springs and listwaenite are associated with dextral releasing bends within the fault system, as well as a basalt intrusion of probable Oligocene age. A structural transect through the Frontal Range along the superbly exposed Wadi Bani Kharous (Jabal Akhdar Dome) revealed that extension affected the Frontal Range at least 2.5 km south of the Frontal Range Fault. Also here, bedding-parallel shearing is important, but not exclusive. A late Cretaceous thrust was extensionally reactivated by a branch fault of the Frontal Range Fault. Extension may be ductile (limestone mylonites), ductile and brittle (ooid deformation, boudinaged belemnite rostra, shear bands) or brittle. Extension is heterogeneously distributed within the Frontal Range. Extension is mainly related to orogenic/gravitational collapse of the Oman Mountains. Collapse may have been associated with isostatic rebound and rise of the two domes. In the western part of the study area, the Frontal Range Fault has a listric morphology. It is probably horizontal at a depth of 15 km below the Batinah coastal area. The fault seems to use the clay- and tuff-bearing Aruma Group as shear horizon. The depth of 15 km may coincide with the brittle-ductile transition of quartz- and feldspar-rich rocks. Close to this depth, the listric Batinah Coast Fault curves into the Frontal Range Fault. Extension along the Frontal Range and Batinah Coast faults probably reactivated preexisting late Cretaceous thrust faults during post-late Eocene time. The latter fault is likely mechanically related to the Wadi Kabir Fault via the Fanja Graben Fault and the Sunub fault segment. Listwaenite and serpentinite cluster preferably around the extensional faults. The Semail Gap probably functioned as a sinistral transform fault or fault zone during the Permian.

Evaluation of subsurface infiltration and displacement in a subsidence-reactivated normal fault in the Aguascalientes Valley, Mexico

In this study, the main hydromechanical characteristics of a portion of the Oriente fault, in the valley of Aguascalientes, Mexico, are analyzed and discussed. This discontinuity corresponds to a normal fault that was originated before the formation of the Aguascalientes graben. However, its recent activity and potential reactivation may be directly linked to the land subsidence currently occurring in the center of the valley. A 1-year campaign to monitor deformation in two transects perpendicular to this fault indicates continuous deformation activity with maximum vertical descending values of 43 mm in the hanging wall. On the other hand, a fieldwork procedure to determine the geologic structure of the fault zone and to establish the infiltration patterns of a selected point in the fault was performed as well. This field test consisted of analyzing the resistivity patterns of profiles across and along the fault, implemented before, during and after pouring groundwater into the fault and monitoring the fluids movement through the fault zone. Results suggest that the fault contains three perpendicular fault branches in a distance of 80 m, portraying a potential domino fault system. The high infiltration capacity of the fault opening allowed the rapid intrusion of water into the subsoil, and the distinguishable changes in electrical resistivity in the profiles parallel to the fault plane suggest that the infiltrating water goes down into the soil through the fault plane or adjacent to it.

A Cycle Voltage Measurement Method and Application in Grounding Grids Fault Location

The corrosion of grounding grids can result in a grounding accident of a power system, and much attentions has been concentrated on the method used to detect a corrosion fault in a grounding grid, in which the methods of voltage measurement and magnetic field measurement are usually used. In this paper, a cycle voltage measurement method and L-curve regularization method are proposed to locate the faults in grounding grids. The L-curve method was used to select the appropriate regularization parameter, which can effectively balance the error and stability of the solution to the inverse problem. The uncertainty of the solution due to the ill-posed problem in the inverse problem has been well-solved. Experiments were conducted in a laboratory with two network types. In addition, a field experiment was carried out in a 110-kV substation. Both of the results showed that the method can effectively locate a branch fault with a single branch and multiple branches in the grounding grids.

A tectonized ultramafic-mafic-pelitic package in Stockbridge, Vermont: Metamorphism resulting from subduction and exhumation

A tectonized ultramafic-mafic-pelitic package southwest of the Burgess Branch Fault Zone in the Rowe/Prospect Rock slice in Stockbridge, Vermont preserves Taconian subduction zone metamorphism. The polydeformed package consists of carbonatized and chloritized serpentinite lozenges that are faulted between graphitic phyllite and an intercalated zone of mafic greenstones and pelitic schists that retain primarily Taconian structures. Amphiboles zoned chemically in greenstones display decreases in PL (NaM4) and TK (AlVI + Fe3+ + 2Ti + Cr) from cores to rims. Pseudosection and amphibole isopleth calculations show that different greenstone bodies experienced peak subduction zone metamorphism at different depths between ∼19 and 32 Km (0.55–0.95 GPa) and/or at different temperatures between ∼425 and 500 °C. Barroisite and winchite cores preserve the highest pressure and lowest temperature peak metamorphism, which is interpreted as lower blueschist facies. All greenstones followed decompression cooling paths to lower greenschist facies where actinolite rims grew. Assembly of the ultramafic-mafic-pelitic package probably occurred in a Taconian exhumation channel containing mantle serpentinite, oceanic crust, and clastic rocks of the Laurentian margin and Iapetan Ocean basin.

Dynamic rupture propagation on geometrically complex fault with along-strike variation of fault maturity: insights from the 2014 Northern Nagano earthquake

Understanding the effect of the complex fault geometry on the dynamic rupture process and discriminating it from the complexity originating from the rheological properties of faults, is an essential subject in earthquake science. The 2014 Northern Nagano earthquake, which occurred near the end zone of a major active fault system, provided unique observations that enabled us to investigate both the detailed geometrical fault structure and surface deformation patterns as well as the temporal sequence led up from a prominent foreshock activity. We first develop a geometrical fault model with a substantial variation along strike, and a model for the regional stress field, which is well constrained by the observations. This significant along-strike variation in fault geometry probably reflects the difference of fault maturity at the end zone of the complex fault system. We used this model in order to conduct a set of dynamic rupture simulations using the highly efficient spatiotemporal boundary integral equation method. Based on our simulations, we show that the observed surface deformation can be reasonably explained as the effect of the non-planar fault geometry with a number of branch faults and bends.Graphical abstract.

野島断層の分岐断層（浅野断層）中軸部物質の高速摩擦特性と摩擦発熱過程

野島断層の分岐断層（浅野断層）中軸部物質の高速摩擦特性と摩擦発熱過程

Experimental study of different modes of block sliding along interface. Part 2. Field experiments and phenomenological model of the phenomenon

The paper reports the results of field experiments on studying different modes of gravitational sliding of a block on the natural fault surface. Various materials were used as interface filler to model the whole range of deformation events that can be arbitrarily divided into three groups: accelerated creep, slow slip, and dynamic slip. The experiments show that the type of modeled deformation events is defined by both structural parameters of contact between blocks and material composition of the contact filler. Foundations for a new geomechanical model of occurrence of different-type dynamic events were developed. The model is based on the idea that “contact spots” form subnormally to the crack edges during shear deformation; the “spots” are clusters of force mesostructures whose evolution governs the deformation mode. The spatial configuration of “contact spots” remains unchanged during the entire “loading-slip” cycle but changes after the dynamic event occurrence. The destroyed force mesostructures can be replaced by similar structures under intergranular interaction forces when the external influence is fully compensated. Unless “contact spots” are incompletely destroyed, the deformation process dynamics is defined by their rheology. The migration of “contact spots” during deformation of a crack filled with heterogeneous material causes changes in deformation parameters and transformation of the mode itself due to changing rheology of local contact areas between blocks. It is found by fractal analysis that in order for dynamic slip to occur, spatially structured “contact spots” characterized by low fractal dimension must be formed; slow slip events can exist only in a certain parametric domain called the “dome of slow events”. It is found that the probability of slow slip occurrence is higher on fault regions characterized by maximum fractal dimension values: fault tips, fault branching and fault intersection zones.

Time series analysis of the NOANET CGPS stations

The National Observatory of Athens has begun installing permanent GPS stations on February 2006 including a EUREF permanent station in Attica, NOA1. Currently the National Observatory of Athens operates 20 continuous GPS stations around Greece all sampling at 1-s and transmitting real-time data to Athens. Several stations also sample at 0.2-s (5 Hz) and record the data in the ring buffer for a period of 1-2 days. Their location is carefully selected so that both geological and seismotectonic criteria are fulfilled. All stations are situated close to major seismogenic structures of Greece such as the Cephalonia Transform Fault (CTF) in the Ionian Sea (VLSM, PONT, SPAN, KIPO), and the two North Anatolian Fault branches in the North Aegean Sea (PRKV, LEMN ). We describe the CGPS data archiving and processing procedures, used to combine into a uniform velocity solution the observations of all the NOANET stations, accounting for the seasonal (annual and semiannual) signals, and considering the off-sets in the coordinate time-series.

Evolution of the Median Tectonic Line fault zone, SW Japan, during exhumation

Like many crustal-scale fault zones, the Median Tectonic Line (MTL) fault zone in Japan preserves fault rocks that formed across a broad range of physical conditions. We examined the architecture of the MTL at a large new outcrop in order to understand fault behaviours under different crustal levels. The MTL here strikes almost E–W, dips to the north, and juxtaposes the Sanbagawa metamorphic rocks to the south against the Izumi Group sediments to the north. The fault core consists mainly of Sanbagawa-derived fault gouges. The fault zone can be divided into several structural units, including two slip zones (upper and lower slip zones), where the lower slip zone is more conspicuous. Crosscutting relationships among structures and kinematics indicate that the fault zone records four stages of deformation. Microstructures and powder X-ray diffraction (XRD) analyses indicate that the four stages of deformation occurred under different temperature conditions. The oldest deformation (stage 1) was widely distributed, and had a top-to-the-east (dextral) sense of slip at deep levels of the seismogenic zone. Deformation with the same sense of slip, then became localised in the lower slip zone (stage 2). Subsequently, the slip direction in the lower slip zone changed to top-to-the-west (sinistral-normal) (stage 3). The final stage of deformation (stage 4) involved top-to-the-north normal faulting along the two slip zones within the shallow crust (near the surface). The widely distributed stage 1 damage zone characterises the deeper part of the seismogenic zone, while the sets of localised principal slip zones and branching faults of stage 4 characterise shallow depths. The fault zone architecture described in this paper leads us to suggest that fault zones display different behaviours at different crustal levels.

Splay fault branching from the Hikurangi subduction shear zone: Implications for slow slip and fluid flow

AbstractPrestack depth migration data across the Hikurangi margin, East Coast of the North Island, New Zealand, are used to derive subducting slab geometry, upper crustal structure, and seismic velocities resolved to ∼14 km depth. We investigate the potential relationship between the crustal architecture, fluid migration, and short‐term geodetically determined slow slip events. The subduction interface is a shallow dipping thrust at <7 km depth near the trench and steps down to 14 km depth along an ∼18 km long ramp, beneath Porangahau Ridge. This apparent step in the décollement is associated with splay fault branching and coincides with a zone of maximum slip (90 mm) inferred on the subduction interface during slow slip events in June and July 2011. A low‐velocity zone beneath the plate interface, updip of the plate interface ramp, is interpreted as fluid‐rich overpressured sediments capped with a low permeability condensed layer of chalk and interbedded mudstones. Fluid‐rich sediments have been imbricated by splay faults in a region that coincides with the step down in the décollement from the top of subducting sediments to the oceanic crust and contribute to spatial variation in frictional properties of the plate interface that may promote slow slip behavior in the region. Further, transient fluid migration along splay faults at Porangahau Ridge may signify stress changes during slow slip.

Prims-Aided Dijkstra Algorithm for Adaptive Protection in Microgrids

Decentralization of electric power is possible with the penetration of distributed generators (DGs) in the microgrid (MG) network. Reconfiguration of MG poses a key challenge in identifying suitable protection schemes for varying the topology of the network. In this paper, a central protection center (CPC) is incorporated whose function is to monitor the MG continuously, identify fault occurrence, and locate the exact faulted branch. The proposed Prim-aided Dijkstra algorithm executed continuously in the CPC is responsible for identifying the current topology of the network and aids in identifying the shortest route from the faulted point to the nearest operating source. The CPC is also responsible for adaptively varying the settings of the relays existing in the shortest path identified based on their selectivity levels. This heuristic algorithm is validated on IEEE 21-bus and 40-bus MG test systems for all possible topologies and faults. The proposed algorithm is capable of clearing the fault by disconnecting minimum portion of the network and ensuring continuity of supply to a majority of loads.

Detailed inventory mapping and spatial analyses to landslides induced by the 2013 Ms 6.6 Minxian earthquake of China

On July 22, 2013, an earthquake (Ms 6.6) occurred in Minxian, Gansu Province of China, causing a large number of landslides. Based on high resolution remote sensing images before and after this event, we made the visual interpretation to these coseismic landslides, and prepared a detailed inventory. The inventory registers totally 6 478 landslides in the study area. Of them, 3 322 landslides are larger than 100 m2. Based on 5 m resolution DEM, these landslides were used to perform spatial analyses using landslide number density (LND) and landslide area percentage (LAP). The results show that the highest LND and LAP values are in the elevation range of 2 300–2 500 m and steeper slopes. Slopes facing E, SE, S and SW directions, slopes with larger absolute curvature values, ridges, scopes of gravel beds of Late Pleistocene (Qp) and the VIII-degree seismic intensity are more prone to sliding with high LND and LAP values. The largest LND and LAP values are in the scopes of 0.08 and 0.24 g, respectively. According to landslide distribution, we infer that F2-2 branch of Lintan-Dangchang fault is the seismogenic fault. With the increasing distances to this branch fault and drainages, LND and LAP values tend to decrease.

Earthquake Potential of Active Faults in Taiwan from GPS Observations and Block Modeling

Research Article| October 19, 2016 Earthquake Potential of Active Faults in Taiwan from GPS Observations and Block Modeling Wu‐Lung Chang; Wu‐Lung Chang aDepartment of Earth Sciences, National Central University, 300, Zhongda Road, Taoyuan 32001, Taiwanwuchang@ncu.edu.tw Search for other works by this author on: GSW Google Scholar Kuo‐En Ching; Kuo‐En Ching bDepartment of Geomatics, National Cheng Kung University, 1, University Road, Tainan 701, Taiwan Search for other works by this author on: GSW Google Scholar Chiou‐Hsien Lee; Chiou‐Hsien Lee aDepartment of Earth Sciences, National Central University, 300, Zhongda Road, Taoyuan 32001, Taiwanwuchang@ncu.edu.tw Search for other works by this author on: GSW Google Scholar Yi‐Rui Lee; Yi‐Rui Lee cSinotech Engineering Consultants, Inc., 14F, 171, Section 5, Nanking E. Road, Taipei 105, Taiwan Search for other works by this author on: GSW Google Scholar Chi‐Fang Lee Chi‐Fang Lee aDepartment of Earth Sciences, National Central University, 300, Zhongda Road, Taoyuan 32001, Taiwanwuchang@ncu.edu.tw Search for other works by this author on: GSW Google Scholar Seismological Research Letters (2016) 87 (6): 1274–1286. https://doi.org/10.1785/0220160094 Article history first online: 14 Jul 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn MailTo Tools Icon Tools Get Permissions Search Site Citation Wu‐Lung Chang, Kuo‐En Ching, Chiou‐Hsien Lee, Yi‐Rui Lee, Chi‐Fang Lee; Earthquake Potential of Active Faults in Taiwan from GPS Observations and Block Modeling. Seismological Research Letters 2016;; 87 (6): 1274–1286. doi: https://doi.org/10.1785/0220160094 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentBy SocietySeismological Research Letters Search Advanced Search ABSTRACT Taiwan is located at the boundary between the Philippine Sea plate and the passive continental margin of the Eurasian plate and is one of the most seismically active regions in the world. In an attempt to evaluate the seismogenic potential of active faults in Taiwan, we separated the region into 34 blocks with 27 known active faults as their boundaries and employed a 3D elastic block modeling method to invert the Global‐Positioning‐System‐measured surface deformation for block rotations and the fault coupling. Additional constraints from an up‐to‐date dataset of geologic fault‐slip rates were introduced to reconcile the discrepancy between the geodetically and geologically determined long‐term slip rates. Our results show that the Hsinhua fault and the southern part of the Longitudinal Valley fault may be weakly coupled near the surface and therefore experience shallow creeping in the interseismic period. The slip‐deficit rates, which relate to how fast the elastic strain is accumulated on faults, are relatively low (0.8–2.2 mm/yr) for faults in northern Taiwan compared with up to 4 mm/yr in the Western foothill of the central and southwestern Taiwan. Evaluations of earthquake potential based on our new modeling results indicate that the frontal thrust and the westernmost branch faults of central Taiwan and the northern Longitudinal Valley fault of eastern Taiwan are capable of generating Mw 6.0–7.3 earthquakes in the next few decades. You do not have access to this content, please speak to your institutional administrator if you feel you should have access.

Secondary Fault Activity of the North Anatolian Fault near Avcilar, Southwest of Istanbul: Evidence from SAR Interferometry Observations

Strike-slip faults may be traced along thousands of kilometers, e.g., the San Andreas Fault (USA) or the North Anatolian Fault (Turkey). A closer look at such continental-scale strike faults reveals localized complexities in fault geometry, associated with fault segmentation, secondary faults and a change of related hazards. The North Anatolian Fault displays such complexities nearby the mega city Istanbul, which is a place where earthquake risks are high, but secondary processes are not well understood. In this paper, long-term persistent scatterer interferometry (PSI) analysis of synthetic aperture radar (SAR) data time series was used to precisely identify the surface deformation pattern associated with the faulting complexity at the prominent bend of the North Anatolian Fault near Istanbul city. We elaborate the relevance of local faulting activity and estimate the fault status (slip rate and locking depth) for the first time using satellite SAR interferometry (InSAR) technology. The studied NW-SE-oriented fault on land is subject to strike-slip movement at a mean slip rate of ~5.0 mm/year and a shallow locking depth of <1.0 km and thought to be directly interacting with the main fault branch, with important implications for tectonic coupling. Our results provide the first geodetic evidence on the segmentation of a major crustal fault with a structural complexity and associated multi-hazards near the inhabited regions of Istanbul, with similarities also to other major strike-slip faults that display changes in fault traces and mechanisms.

High Resistant Sand Injected Marl and Low Resistant Damaged Marl to Locate and Characterize the Thénia Fault Zone in Boumerdes City (North-Central Algeria)

The purpose of this study was to locate and characterize the Thenia Fault Zone (TFZ) in the urban area of Boumerdes city; geological and electrical resistivity tomography surveys have targeted the Plaisancian marl and its Quaternary cover. As a whole, data indicate a complex near-vertical fault zone with an asymmetric and zoned internal structure of at least 150 m wide and with a straight N120° overall trending. The fault zone is traversed with two elongated parallel fault branches (FB1 and FB2), generally, 70 m distant from each other. These fault branches locate two intense damage zones (IDZs) of 10–15 m thick each, situated at the margin of two damage zones each having a thickness of several tens of meters. Downward sand injections into IDZs during Pleistocene epoch, possible pulverization of Plaisancian marl rocks, systematic deflection of actual stream channels, and vertical displacement of at least 30 m affecting Quaternary alluvial deposits show that the area would have undergone active tectonic driven by the TFZ.