A Subsurface Geologic Feature Inferred from Relocation of Local Earthquakes in Al-Refaei District, Southern Iraq

2020 ◽  
Vol 54 (1A) ◽  
pp. 35-43
Author(s):  
Ali Ramthan
Keyword(s):  
High Frequency ◽  
Tectonic Setting ◽  
Arabian Plate ◽  
Stress Regime ◽  
Shallow Subsurface ◽  
Linear Feature ◽  
Recording Station ◽  
Communications System ◽  
System Power ◽  
Southern Iraq

For the last two decades, the District of Al-Refaei, southern Iraq, experienced several small to moderate size earthquakes that seem to be clustered in a relatively small area. The initial locations of these earthquakes from the available local and international bulletins show scattered events without any clear structural patterns. A seven-elements seismic array was installed for the period 2014 to 2018 to monitor this activity. Each element of the array consists of three-component Geospace GS11d high-frequency (4.5 Hz) geophone, a solar system power source, and telemetry communications system to transmit data to a central recording station. During the period of monitoring, the array recorded more than 56 earthquakes having a range of magnitude between 1.5 ML to 4.7 mb. Large number of the low magnitude earthquakes were not detected by other monitoring agencies; however, they were recorded by the array. Fifty-six of the most clearly recorded earthquakes were screened for relocation and analysis. Out of the 56 screened earthquakes, 35 were detected by the array alone. The majority of the selected earthquakes having their initial locations within the array. This improves the relocation process and increase accuracy. The relocated earthquakes express a clear pattern of a linear feature which strikes in the northwest-southeast direction. The direction of the newly inferred pattern coincides with the general tectonic setting of Iraq as it is parallel to Zagros suture zone and the general stress regime of the Arabian Plate. The depth of the relocated earthquakes ranges from about 3.9km to 8.9km. This indicates that these earthquakes occur along a shallow subsurface fault that was not mapped before.

scholarly journals VLA Polarization Observation of the Radio Arc at 15 Ghz

1989 ◽  
Vol 136 ◽  
pp. 269-274 ◽  
Author(s):  
M. Inoue ◽  
E. Fomalont ◽  
M. Tsuboi ◽  
F. Yusef-Zadeh ◽  
M. Morris ◽  
...  
Keyword(s):  
Magnetic Field ◽  
High Frequency ◽  
High Spatial Resolution ◽  
Intrinsic Polarization ◽  
Linear Feature ◽  
Field System ◽  
Polarization Observation ◽  
Field Systems ◽  
Relativistic Particles ◽  
Accelerated Particles

Polarization measurements of the radio Arc were made with the VLA at 15 GHz. High frequency polarimetry made with high spatial resolution minimizes Faraday depolarization and reveals polarized filaments which correspond to the predominant filaments of the radio Arc. We notice a peculiar linear feature in the polarization map (“thorns”) which suggests the presence of a second magnetic field system. The total intensity maps show no evidence for an interaction between the two field systems, so the thorns may be foreground magnetized structures. However, if the two magnetic field systems do interact, it would allow a model in which the acceleration of relativistic particles takes place at their intersection. The accelerated particles would flow toward both ends of the radio Arc, and account for the intrinsic polarization observed along the entire length of the system. Thermal electrons responsible for the Faraday depolarization occuring at longer wavelengths may be supplied by the interaction of the streams of relativistic particles with relatively dense, ambient thermal clouds.

scholarly journals New records of planktonic foraminifera in the Shuaiba Formation (Aptian Age), Mesopotamian plain, South of Iraq

2019 ◽  
pp. 1322-1335
Author(s):  
Zain Alabdeen A. Al-Shawi ◽  
Maher M. Mahdi ◽  
Abbas H. Mohammed
Keyword(s):  
New Records ◽  
Planktonic Foraminifera ◽  
Oil Fields ◽  
The Other ◽  
Arabian Plate ◽  
History Of ◽  
South Of Iraq ◽  
The Many ◽  
First Time ◽  
Southern Iraq

Shuaiba Formation is an important formation in Iraq, because of their deposition in the important period during the geological history of Arabian plate. The study is focused on a number of selected wells from several fields in southern Iraq, despite the many of oil studies to Shuaiba Formation but it lacks to paleontological studies. Four selected wells are chosen for the current study, Zb-290, Ru-358, R-624, WQ1-353, the selected wells are located within different fields, these are Zubair, Rumaila and West Qurna Oil Fields. In this study fourteen species followed to genus Hedbergella were discovered for first time as well as three genera followed to genus Heterohelix in the Shuaiba Formation at the different oil fields, Hedbergella tunisiensis Range Zone is suggested biozone to the current study, the age of this biozone is Aptian, most of the other genera located within this zone.

The San Salvador earthquake of May 3, 1965

1966 ◽  
Vol 56 (2) ◽  
pp. 561-575
Author(s):  
Cinna Lomnitz ◽  
Rudolf Schultz
Keyword(s):  
Volcanic Activity ◽  
Main Shock ◽  
Tectonic Setting ◽  
Focal Depth ◽  
Building Codes ◽  
General Area ◽  
Populated Area ◽  
Shallow Subsurface ◽  
San Salvador ◽  
Zoning Regulations

abstract The San Salvador earthquake of May 3, 1965 was preceded by a local seismic swarm of three months duration. The main shock was destructive in a densely populated area of not more than 15 km in radius; the same general area was damaged in the earthquakes of 1576, 1659, 1798, 1839, 1854, 1873, 1880, 1917, and 1919. Over 120 casualties were reported. The epicenter has been located on the south rim of the Median Trough, a post-Pliocene structure which accounts for the high seismic and volcanic activity in the region. The observed intensity is attributable to shallow focal depth and to the presence of thick inhomogeneous beds of fluviatile pumice. The tectonic setting and shallow subsurface factors should be recognized in future building codes and zoning regulations.

Determination of high-frequency attenuation characteristic of coda waves in the central region of Nepal Himalaya

2020 ◽  
Vol 60 ◽  
pp. 75-86
Author(s):  
Thakur Prasad Kandel ◽  
Masumi Yamada ◽  
Prakash Pokhrel
Keyword(s):  
Quality Factor ◽  
Central Region ◽  
High Frequency ◽  
Wave Attenuation ◽  
Tectonic Setting ◽  
Coda Wave ◽  
Window Length ◽  
Seismic Stations ◽  
High Attenuation ◽  
Coda Wave Attenuation

The high-frequency coda wave attenuation in the central region of Nepal, in and around the Kathmandu valley, is estimated using vertical component seismograms of local earthquakes recorded at 16 different seismic stations of NAMASTE array. The estimated result is expressed in terms of Qc, quality factor (inverse of coda wave attenuation). The value of coda quality factor (Qc) is estimated at eight central frequencies of 1.5, 3.0, 6.0, 9.0, 12.0, 15.0, 18.0, and 21.0 Hz through four different coda window length from 20 to 50 s at 10 s interval by using the single backscattering model. The value of coda Qc obtained from this study, shows a clear dependence on a frequency according to the power relation, Qc (f)= Q0 f n, where Q0  is Qc  at 1 Hz, and f is frequency and n represents the degree of frequency dependence. The mean value of Qc of 16 different seismic stations was obtained as (110 ± 10.6) f 1.03±0.03 at 30 s coda window length, which represents the high attenuation characteristics of the study area, and attenuation decreases with increasing central frequency. Qo increases from 73.1 ± 10.1 to 156.1 ± 13.6 and n decreases from 1.12 ± 1.05 to 0.92±0.03 when the coda window length increases from 20 to 50 s. It is concluded that the study area is tectonically very active, highly heterogeneous, and heterogeneity decrease with depth. The coda Q obtained in this study is compatible with the result obtained in the region having a similar tectonic setting.

scholarly journals High frequency GPS bursts and path-level analysis reveal linear feature tracking by red foxes

2019 ◽  
Vol 9 (1) ◽  
Author(s):  
Richard Bischof ◽  
Jon Glenn Omholt Gjevestad ◽  
Andrés Ordiz ◽  
Katrine Eldegard ◽  
Cyril Milleret
Keyword(s):  
High Frequency ◽  
Feature Tracking ◽  
Red Foxes ◽  
Linear Feature ◽  
Level Analysis

Vs-0 Correction Factors for Input Ground Motions used in Seismic Site Response Analyses

2019 ◽  
pp. 122315EQS188M
Author(s):  
Ashly Cabas ◽  
Adrian Rodriguez-Marek
Keyword(s):  
High Frequency ◽  
Site Response ◽  
Traditional Approach ◽  
Ground Motions ◽  
Spectral Energy ◽  
Correction Factors ◽  
Seismic Site Response ◽  
Recording Station ◽  
Shallow Crust

Input motions used in seismic site response analyses are commonly selected based on similarities between the shear wave velocity (Vs) at the recording station, and the reference depth at the site of interest (among other aspects such as the intensity of the expected ground motion). This traditional approach disregards the influence of the attenuation in the shallow crust on site response. Given that this attenuation (damping) can be characterized by the distance-independent high-frequency attenuation parameter 0, a Vs-0 correction framework for input motions is proposed to render them compatible with the assumed properties of the reference depth at the site. The proposed correction factors were applied to a subset of recordings from the KiK-net database, and compared to traditional deconvolution. Results indicate that Vs-0 corrected motions outperform deconvolved motions in the characterization of the spectral energy in the high-frequency range. However, motions recorded at sites with soft deposits are not good candidates for the Vs-0 correction approach. Vs-0 corrections also affect amplification functions which are important in the assessment of site-specific seismic hazards.

scholarly journals A High-Frequency Phase Feature for the Measurement of Magnetic Permeability Using Eddy Current Sensor

2021 ◽  
Author(s):  
Mingyang Lu ◽  
Xiaobai Meng ◽  
Ruochen Huang ◽  
Liming Chen ◽  
Anthony Peyton ◽  
...  
Keyword(s):  
Magnetic Permeability ◽  
High Frequency ◽  
Impedance Measurement ◽  
Destructive Testing ◽  
Zero Crossing ◽  
Linear Feature ◽  
Signal Features ◽  
Fast Processing ◽  
Lift Off ◽  
Phase Term

Electromagnetic sensing has been used for diverse applications of non-destructive testing, including the surface inspection, measurement of properties, object characterization. However, the measurement accuracy could be significantly influenced by the lift-off between sensors and samples. To address the issue caused by lift-offs, various strategies have been proposed for the permeability measurement of ferromagnetic steels, which mainly involves different sensor designs and signal features (e.g., the zero-crossing feature). In this paper, a single high-frequency scenario for the permeability retrieval is introduced. By combining the signal of two sensing pairs, the retrieval of magnetic permeability is less affected by the lift-off of sensors. Unlike the previous strategy on reducing the lift-off effect (directly taking the phase term out of the integration) using the Dodd-Deeds analytical method, the proposed method is based on a high-frequency linear feature of the phase term. Therefore, this method has the merit of high accuracy and fast processing for the permeability retrieval (a simplified version of Dodd-Deeds analytical formulas after the integration). Experimental measurement has been carried out on the impedance measurement of designed sensors interrogating ferromagnetic dual-phase steels. For sensor lift-offs of up to 10 mm, the error of the permeability retrieval is controlled within 4 % under the optimal frequency.

Improving System Performance with eGaN® FETs in DC-DC Applications

2013 ◽  
Vol 2013 (1) ◽  
pp. 000764-000769 ◽  
Author(s):  
David Reusch ◽  
Johan Strydom ◽  
Alex Lidow
Keyword(s):  
System Architecture ◽  
Power Distribution ◽  
High Frequency ◽  
Power Transistors ◽  
Enhancement Mode ◽  
Power Bus ◽  
Isolated Point ◽  
Bus Architecture ◽  
Popular Power ◽  
System Power

The intermediate bus architecture (IBA) is currently the most popular power system architecture in computing and telecommunications equipment. It typically consists of a +48 V system power distribution bus that feeds on-board isolated converters, which in turn supply power to a 12 V power bus. From the 12 V power bus, the final power is delivered to the end loads by regulated non-isolated point of load (POL) converters. In this paper we demonstrate substantial system gains using enhancement mode gallium nitride power transistors in high frequency isolated and non-isolated DC-DC converters. These transistors, also known as eGaN® FETs, have been commercially available for over three years and are making significant inroads replacing the aging silicon power MOSFET.

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