scholarly journals Using the ERT method in tectonically active areas: hints from Southern Apennine (Italy)

2008 ◽  
Vol 19 ◽  
pp. 61-65 ◽  
Author(s):  
A. Giocoli ◽  
P. Burrato ◽  
P. Galli ◽  
V. Lapenna ◽  
S. Piscitelli ◽  
...  
Keyword(s):  
Active Faults ◽  
Electrode Spacing ◽  
Borehole Data ◽  
Geometrical Characterization ◽  
Resistivity Tomography ◽  
Structural Setting ◽  
Tectonically Active ◽  
Fault Trace ◽  
Fault Scarps ◽  
Depositional Setting

Abstract. Electrical Resistivity Tomography (ERT) method has been used to study two tectonically active areas of southern Apennine (Caggiano Faults and Ufita Basin). The main aim of this job was to study the structural setting of the investigated areas, i.e. the geometry of the basins at depth, the location of active faults at surface, and their geometrical characterization. The comparison between ERT and trench/drilling data allowed us to evaluate the efficacy of the ERT method in studying active faults and the structural setting of seismogenic areas. In the Timpa del Vento intermontane basin, high resolution ERT across the Caggiano Fault scarps, with different arrays, electrode spacing (from 1 to 10 m) and penetration depth (from about 5 to 40 m) was carried out. The obtained resistivity models allowed us to locate the fault planes along the hillslope and to gather information at depth, as later confirmed by paleoseismological trenches excavated across the fault trace. In the Ufita River Valley a 3560-m-long ERT was carried out across the basin, joining 11 roll-along multi-channel acquisition system with an electrode spacing of 20 m and reaching an investigation depth of about 170 m. The ERT allowed us to reconstruct the geometry and thickness of the Quaternary deposits filling the Ufita Valley. Our reconstruction of the depositional setting is in agreement with an interpretative geological section based on borehole data.

Discovery of Ulaanbaatar Fault: A New Earthquake Threat to the Capital of Mongolia

2020 ◽  
Vol 92 (1) ◽  
pp. 437-447
Author(s):  
Yasuhiro Suzuki ◽  
Takashi Nakata ◽  
Mitsuhisa Watanabe ◽  
Sukhee Battulga ◽  
Dangaa Enkhtaivan ◽  
...  
Keyword(s):  
Active Fault ◽  
Active Faults ◽  
Plate Boundaries ◽  
Safety Measures ◽  
Fault Trace ◽  
Seismic Hazard Map ◽  
Fault Scarps ◽  
Japan Aerospace Exploration Agency ◽  
Scope Interpretation ◽  
Large Earthquakes

Abstract Destructive large earthquakes occur not only along major plate boundaries but also within the interior of plates. To establish appropriate safety measures, identifying intraplate active faults and the potential magnitude of associated earthquakes is essential before an earthquake occurs. This study was conducted to document the geomorphic expression of a previously unrecognized 50-km-long active fault in Ulaanbaatar, the capital of Mongolia. Mapping of the fault was accomplished using the Advanced Land Observation Satellite elevation dataset provided by Japan Aerospace Exploration Agency (JAXA), a stereo-scope interpretation of CORONA satellite images, the emplacement of trenches across the fault trace, and field study. The Ulaanbaatar fault (UBF) is marked by fault scarps on the surface and left-lateral stream deflections. The fault displaces late Pleistocene deposits and is thus considered to be active. Based on the length of the fault, the UBF is believed to be capable of causing earthquakes with magnitudes greater than M 7 and subsequent associated damage to buildings and heavy causalities within the metropolitan area. We strongly suggest that building resistance requirements in Ulaanbaatar should be revised to mitigate for the potential of extensive seismic damage. The results of this study can be used to revise the seismic hazard map and stipulate a new disaster prevention strategy to improve public safety in Ulaanbaatar. It is also possible that there may be other active faults in the vicinity of Ulaanbaatar, and these require investigation.

scholarly journals Geophysical evi-dence of the 1912 earthquake rupture along the central fault system of the Acambay Graben, Central Mexico

2021 ◽  
Vol 73 (2) ◽  
pp. A250121
Author(s):  
Pierre Lacan ◽  
Claudia Arango-Galván
Keyword(s):  
Electrical Resistivity ◽  
Active Faults ◽  
Fault System ◽  
Resistivity Tomography ◽  
Sedimentary Environments ◽  
San Pedro ◽  
Horizontal Variation ◽  
Endorheic Basin ◽  
Fault Trace ◽  
The One

In this work, we have applied two geophysical techniques in two different areas of potential interest for paleoseismological assessment of the active faults of the Acambay graben. The main goal was to localize segments of buried faults suspected to break the surface during the 1912 Acambay Earthquake, in order to (1) identify favorable sites for paleoseismological investigation purpose and (2) extrapolate the data obtained with a paleoseismic trenching. On the one hand, Electromagnetic Induction (EMI) Method was used to map the horizontal variation of the apparent resistivity in order to detect the 1912 surface rupture of the Temascalcingo fault in the alluvial plain of the Lerma River. On the other hand, within a volcanic edifice, the Electrical Resistivity Tomography (ERT) tech-nique was used to characterize the electrical resistivity distribution along a profile in or-der to detect and localize the San Pedro fault, partially buried in a Holocene sedimentary filling of a small endorheic basin. Results of these studies allow defining location and orientation of the structures that potentially broke the surface during the 1912 earthquake and are partially hidden by recent deposits filling the tectonic depressions. Good correla-tion between ERT subsurface to deep imagery of faults and a trench survey which cuts across the San Pedro fault trace, illustrate the pertinence to use such techniques for pale-oseismological investigation purpose in volcano-sedimentary environments.

scholarly journals Identifying Changes in Sediment Texture along an Ephemeral Gravel-Bed Stream Using Electrical Resistivity Tomography 2D and 3D

2021 ◽  
Vol 11 (7) ◽  
pp. 3030
Author(s):  
Marcos A. Martínez-Segura ◽  
Carmelo Conesa-García ◽  
Pedro Pérez-Cutillas ◽  
Pedro Martínez-Pagán ◽  
Marco D. Vásconez-Maza
Keyword(s):  
Electrical Resistivity ◽  
Cross Sections ◽  
Electrical Resistivity Tomography ◽  
Environmental Changes ◽  
Subsurface Layer ◽  
Sediment Texture ◽  
Borehole Data ◽  
Resistivity Tomography ◽  
Gravel Bed ◽  
Basin Scale

Differences in deposit geometry and texture with depth along ephemeral gravel-bed streams strongly reflect fluctuations in bedload which are due to environmental changes at the basin scale and to morphological channel adjustments. This study combines electrical resistivity tomography (ERT) with datasets from borehole logs to analyse the internal geometry of channel cross-sections in a gravel-bed ephemeral stream (southeast Spain). The survey was performed through longitudinal and transverse profiles in the upper channel stretch, of 14 to 30 m in length and 3 to 6 m in depth, approximately. ERT values were correlated with data on sediment texture as grain size distribution, effective grain sizes, sorting, and particle shape (Zingg’s classification). The alluvial channel-fills showed the superposition of four layers with uneven thickness and arrangement: (1) the softer rocky substrate (<1000 Ω.m); (2) a thicker intermediate layer (1000 to 2000 Ω.m); and (3) an upper set composed of coarse gravel and supported matrix, ranging above 2000 Ω.m, and a narrow subsurface layer, which is the most resistive (>5000 Ω.m), corresponding to the most recent armoured deposits (gravel and pebbles). The ERT results coupled with borehole data allowed for determining the horizontal and vertical behaviour of the materials in a 3D model, facilitating the layer identification.

Liquefaction susceptibility maps for the Aqaba–Elat region with projections of future hazards with sea-level rise

2020 ◽  
pp. qjegh2020-039 ◽  
Author(s):  
Abdel-Rahman A. Abueladas ◽  
Tina M. Niemi ◽  
Abdallah Al-Zoubi ◽  
Gideon Tibor ◽  
Mor Kanari ◽  
...  
Keyword(s):  
Sea Level ◽  
Water Table ◽  
Active Faults ◽  
Gulf Of Aqaba ◽  
Susceptibility Map ◽  
Northern Coast ◽  
Borehole Data ◽  
Ground Acceleration ◽  
Liquefaction Susceptibility ◽  
Susceptibility Maps

The cities of Aqaba, Jordan and Elat, Israel are vulnerable to seismic damage because they are built over the active faults of the Dead Sea Transform that are the source of historically destructive earthquakes. A liquefaction susceptibility map was generated for the Aqaba–Elat region. Borehole data from 149 locations and the water table depth were used to calculate effective overburden stress in the Seed–Idriss simplified method. The liquefaction analysis was based on applying a cyclic loading scenario with horizontal peak ground acceleration of 0.3 g in a major earthquake. The liquefaction map, compiled using a GIS platform, shows high and moderate liquefaction susceptibility zones along the northern coast of the Gulf of Aqaba that extend 800 m inland from the shoreline. In Aqaba, several hotels, luxury apartment complexes, archaeological sites, ports and commercial districts are located within high and moderate liquefaction zones. In Elat, the seaport and the coastal hotel district are located within a high susceptibility zone. Most residential areas, schools and hospitals in both cities are located within zones not susceptible to liquefaction based on the methods of this study. The total area with the potential to be liquefied along the Gulf of Aqaba is c. 10 km2. Given predictions for global sea-level, we ran three liquefaction models utilizing projected water table rises of 0.5, 1 and 2 m. These models yielded an increase in the area of high liquefaction ranging from 26 to 49%. Given the high potential of future earthquakes, our liquefaction susceptibility maps should help inform city officials for hazard mitigation planning.

scholarly journals The active tectonic landscape of Lake Ohrid (FYR of Macedonia/Albania)

2014 ◽  
Vol 56 (6) ◽  
Author(s):  
Nadine Hoffmann
Keyword(s):  
Active Faults ◽  
Fault Scarp ◽  
Mass Wasting ◽  
Lake Ohrid ◽  
Slip Rates ◽  
Active Tectonic ◽  
Western Border ◽  
Wine Glass ◽  
Yugoslavian Republic ◽  
Fault Scarps

<p><span style="font-family: CMR10; font-size: medium;">The study area at the Lake Ohrid Basin is located on 693 m a.s.l. at the south-western border of the Former Yugoslavian Republic of Macedonia with Albania. It is a suitable location for neotectonic studies. It exhibits a large variety of morphological expressions associated with the seismic activity of the region. Linear bedrock fault scarps give the relief on both sides of the lake a staircase-like appearance; other features are wine-glass shaped valleys and triangular facets. These often short living features are used to identify active faults and to parameterise palaeoearthquakes (slip rates, subsidence and erosion). According to the results of fault scarp profiling a halfgraben shape of the basin is proposed with the west coast being dominated by mass wasting processes most likely triggered by seismic events.</span></p>

scholarly journals Estimation of absolute stress in the hypocentral region of the 2019 Ridgecrest, California, earthquakes

2020 ◽  
Author(s):  
Yuri Fialko
Keyword(s):  
Seismic Data ◽  
Plate Tectonics ◽  
Active Faults ◽  
Active Regions ◽  
Seismogenic Zone ◽  
Shear Stresses ◽  
Strong Earthquakes ◽  
Frictional Strength ◽  
Tectonically Active ◽  
Weak Fault

Abstract Strength of the upper brittle part of the Earth's lithosphere controls deformation styles in tectonically active regions, surface topography, seismicity, and the occurrence of plate tectonics, yet it remains one of the least constrained and most debated quantities in geophysics. Seismic data (in particular, earthquake focal mechanisms) have been used to infer orientation of the principal stress axes. Here I show that the focal mechanism data can be combined with information from precise earthquake locations to place robust constraints not only on the orientation, but also on the magnitude of absolute stress at depth. The proposed method uses machine learning to identify quasi-linear clusters of seismicity associated with active faults. A distribution of the relative attitudes of conjugate faults carries information about the amplitude and spatial heterogeneity of the deviatoric stress and frictional strength in the seismogenic zone. The observed diversity of dihedral angles between conjugate faults in the Ridgecrest (California, USA) area that hosted a recent sequence of strong earthquakes suggests the effective coefficient of friction of 0.4-0.6, and depth-averaged shear stresses on the order of 25-40 MPa, intermediate between predictions of the "strong" and "weak" fault theories.

Delineating active faults across the Narmada-Son Lineament (NSL), India using the technique of Fracture Induced Electromagnetic Radiation (FEMR)

2021 ◽  
Author(s):  
Shreeja Das ◽  
Jyotirmoy Mallik
Keyword(s):  
Electromagnetic Radiation ◽  
Process Zone ◽  
Active Faults ◽  
Central India ◽  
Earthquake Forecasting ◽  
Tectonic Activity ◽  
Eurasian Plate ◽  
Near Surface ◽  
Crustal Stresses ◽  
Tectonically Active

&lt;p&gt;The Fracture Induced Electromagnetic Radiation (FEMR) technique has gradually progressed in the past decade as a useful geophysical tool to determine the direction and magnitude of recent crustal stresses, visualize the modification and realignment of stresses inside tunnels thus proving to be an important precursor for geohazards, earthquake forecasting, as well as delineate landslide-prone slip planes in unstable regions. Its working principle is based on the generation of geogenic electromagnetic radiation emanating from the brittle rock bodies that are fractured being subjected to an incremental increase of the differential stress in the near-surface of the Earth&amp;#8217;s crust. The &amp;#8220;Process zone&amp;#8221; at the fractured crack tip contains numerous microcracks which subsequently creates dipoles due to the polarization of charges on such microcrack tips which rapidly oscillates emitting FEMR waves of frequencies between KHz to MHz range. The coalescence of the microcracks eventually leads to a macro failure dampening the amplitude of the FEMR pulses. The attenuation of FEMR pulses is comparatively lesser than seismic waves making it a more efficient precursor to potential tectonic activities indicating an upcoming earthquake a few hours/days before the actual event. In the current study, we have attempted to exploit this technique to identify the locations of the potential active faults across the tectonically active Narmada-Son Lineament (NSL), Central India. Although the first tectonic stage involved rifting and formation of the NSL during the Precambrian time, the rifting continued at least till the time of Gondwana deposition. Later, tectonic inversion took place as a result of the collision between the Indian and the Eurasian plate resulting in reverse reactivation of the faults. Episodic reverse movement along NSL caused recurrent earthquakes and linear disposition of the sediments that were deposited at the foothills of the Satpura Horst. Although the origin of East-West trending NSL dates back to the Precambrian time, it is very much tectonically active as manifested by recent earthquakes. The study has been conducted by taking linear FEMR readings across 3 traverses along the NSL which on analysis provides an idea about the potential active faults, their locations, and frequency of occurrence. The accumulation of strain in the brittle rocks that can eventually lead to a macro failure is demarcated as an anomalous increase in the amplitude of the FEMR pulses indicative of an upcoming tectonic episode in the region. To further corroborate the analysis, we have attempted to determine the neo-tectonic activity in the region by calculating the morphometric parameters across the Khandwa-Itarsi-Jabalpur region, Central India. Finally, we attempt to comment on the tectonic evolution of Central India in the recent past. We also encourage researchers to adapt the novel technique of FEMR which is swift, affordable, and feasible compared to conventional techniques deployed to survey the active tectonics of a region.&lt;/p&gt;

scholarly journals Relationship between seismicity and active faults in Thanh Hoa province detected by local seismic network

2021 ◽  
Vol 43 (2) ◽  
pp. 199-219
Author(s):  
Duong T. N. ◽  
Lai Hop Phong ◽  
Pham D. N. ◽  
Chen C. H. ◽  
Dinh V. T.
Keyword(s):  
Seismic Activity ◽  
Active Faults ◽  
Seismic Network ◽  
Local Network ◽  
Ground Acceleration ◽  
Magnetotelluric Data ◽  
Seismogenic Source ◽  
Tectonically Active ◽  
Relationship Of ◽  
The Relationship

Thanh Hoa province belongs to the southwest part of Northwest Vietnam, which is considered a tectonically active region. In the area of Thanh Hoa province, there are three deep-seated tectonic faults, namely Son La-Bim Son, Song Ma, and Sop Cop. As predicted by scientists, these faults are capable of producing credible earthquakes that might be the strongest in the territory of Vietnam. Besides the three main seismogenic sources, in the province, there are other smaller active faults such as Thuong Xuan-Ba Thuoc and Thuong Xuan-Vinh Loc but the relationship of these faults with seismic activity is still rather blurred. This may due to the sparseness of the Vietnamese National Seismic Network which can not record adequately small earthquakes in the area. This paper presents new results of additional monitoring from a local seismic network using 12 Guralp - 6TD broadband seismometers that have been deployed in Thanh Hoa province since November 2009. We found that the Thanh Hoa area is not seismically quiet. The average number of earthquakes recorded by the network has reached 80 - 90 events per year and some of them have magnitude from ML 3.0 to 4.0.By integration of the earthquake epicenters derived from the local network and distribution of active faults, we can detect several earthquakes locating near the three active faults, not only along the main faults but also along its subsidiary faults. We focused on the active faults of Thuong Xuan-Ba Thuoc and Thuong Xuan-Vinh Loc by using the recent results of the gravity, seismic, and magnetotelluric data analyses. Several recorded earthquakes distribute along the two small faults and some of them reach magnitude 3.0 or greater on the ML scale. In this study, the Thuong Xuan-Vinh Loc is recognized as a seismogenic source. To identify seismic hazard potential caused by earthquakes generated from the active faults, segmentation of the Thuong Xuan - Ba Thuoc fault had been done based on geological and geomorphological indications and seismic activity, and then the peak ground acceleration was determined for each fault segment. Besides, a large number of earthquake epicenters do not have a good correlation with a specific fault, especially in the area of Thanh Hoa coastal plain, which is covered by thick layers of Neogene - Quaternary sediment. This shows that there may be hidden active faults in the area which are needed to study further.

scholarly journals Two-dimensional Electrical Resistivity Tomography of Bitumen Occurrence in Agbabu, Southwest Nigeria

2019 ◽  
pp. 1-9
Author(s):  
O. F. Ogunlana ◽  
O. M. Alile ◽  
O. J. Airen
Keyword(s):  
Electrical Resistivity ◽  
Apparent Resistivity ◽  
Electrical Resistivity Tomography ◽  
Electrode Spacing ◽  
Southwestern Nigeria ◽  
Resistivity Tomography ◽  
2D Inversion ◽  
Earth Resistivity ◽  
Southwest Nigeria ◽  
Resistivity Meter

The Electrical Resistivity Tomography (ERT) data was acquired within the area suspected to have high potential for bitumen occurrence using the Wenner-Schlumberger configuration in Agbabu, southwestern Nigeria. PASI 16GL-N Earth resistivity meter instrument was used to acquire data along five (5) traverses with 5m electrode spacing and traverses length of 150m. The apparent resistivity values obtained was processed using RES2DINV software which helped to automatically obtain the 2D inversion model of the subsurface. This study has shown the occurrence of bitumen between the depth of 13.4m and 9.93m for Traverses 1, 2, 3 and Traverses 4, 5 respectively in a 2-Dimensional electrical resistivity images for boreholes with a depth of about 18m. The results indicate that the bitumen is characterized by good lateral continuity and is sufficiently thick for commercial exploitation.

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