The southern Caspian: A compressional depression floored by a trapped, modified oceanic crust"

1983 ◽  
Vol 20 (2) ◽  
pp. 163-183 ◽  
Author(s):  
Manuel Berberian
Keyword(s):  
Oceanic Crust ◽  
Body Wave ◽  
Focal Depth ◽  
Sedimentary Facies ◽  
The Body ◽  
The South ◽  
Time Data ◽  
Late Mesozoic ◽  
Thrust Belts ◽  
Mountain Belts

The south Caspian intracontinental depression, floored by oceanic basement, is a relatively stable block, with minor deformation, surrounded by active fold-thrust belts of arcuate form (Talesh, Alborz, and Kopeh Dagh Mountains), which have undergone intense late Cainozoic crustal shortening. The basin is interpreted as a Neogene–Quaternary "compressional depression," bounded by multi-role mountain-bordering reverse faults, and apparently floored by a late Paleozoic – Triassic or late Mesozoic – early Tertiary "modified oceanic crust" trapped along an old geosuture. It may be a relic of an old (Paleozoic–Triassic) ocean, or else a marginal sea developed behind a Mesozoic–Paleogene ocean, and analysis of geological and geophysical data enables a scheme to be suggested. The general arcuate shape of the Alborz and the Talesh bordering mountain belts follows the pattern of the supposed rigid and thickened ocean crust of south Caspian depression.A tectono-sedimentary study of the south Caspian region, coupled with the body-wave modelling of a recent earthquake along one of the bordering faults, may suggest a possible flattening of the fault with depth (listric thrust), and that the estimate of the focal depth of the regional earthquakes based on teleseismic arrival time data is not accurate. The difference in elevation between the depression and the bordering active fold-thrust belts is caused by a difference in crustal structure and reverse faulting during a dominant compressional tectonic regime.The study may add support to the idea that old continental deep-seated multi-role faults, which have controlled the sedimentary facies and basins during different geological times and were responsible for the formation of the present physiographic feature, are the site of the present seismic activity in the orogenic belts.

Focal mechanism and source depth of earthquakes from body- and surface-wave data

1971 ◽  
Vol 61 (5) ◽  
pp. 1369-1379 ◽  
Author(s):  
Nezihi Canitez ◽  
M. Nafi Toksöz
Keyword(s):  
Surface Wave ◽  
Body Wave ◽  
Source Parameters ◽  
Focal Depth ◽  
Spectral Ratio ◽  
The Body ◽  
Spectral Ratios ◽  
Motion Data ◽  
Wave Data ◽  
Surface Wave Data

abstract The determination of focal depth and other source parameters by the use of first-motion data and surface-wave spectra is investigated. It is shown that the spectral ratio of Love to Rayleigh waves (L/R) is sensitive to all source parameters. The azimuthal variation of the L/R spectral ratios can be used to check the fault-plane solution as well as for focal depth determinations. Medium response, attenuation, and source finiteness seriously affect the absolute spectra and introduce uncertainty into the focal depth determinations. These effects are nearly canceled out when L/R amplitude ratios are used. Thus, the preferred procedure for source mechanism studies of shallow earthquakes is to use jointly the body-wave data, absolute spectra of surface waves, and the Love/Rayleigh spectral ratios. With this procedure, focal depths can be determined to an accuracy of a few kilometers.

scholarly journals Seismic Evidence of Pop-up Tectonics Beneath the Shillong Plateau Area of Northeast India

2022 ◽  
Author(s):  
A. P. Singh ◽  
O. P. Mishra ◽  
O. P. Singh
Keyword(s):  
Seismic Tomography ◽  
High Velocity ◽  
Body Wave ◽  
The Body ◽  
Depth Range ◽  
Seismic Velocities ◽  
Shillong Plateau ◽  
Time Data ◽  
High Quality ◽  
Velocity Anomalies

Abstract Our detailed analysis of high-quality arrival time data recorded by the local seismographic network using three-dimensional seismic tomography of the Shillong Plateau region using high-quality arrival times of the body wave phases recorded at a dense temporary seismic network. This technique is used to understand the heterogeneities of the crust and its implications for pop-up tectonics characterizing evaluation the of the Shillong Plateau. We investigated an area covering ~150 ×100 km2 that revealed seismicity to be confined in a depth range ≤ 60 km. High - velocity anomalies in the upper crust appear to be responsible for intense small to moderate seismic activity in the region. Crustal seismic velocities inferred from 3-D seismic tomography showed significant lateral heterogeneities beneath the lithosphere of the Shillong Plateau. High-velocity anomalies in the uppermost crust, interpreted as the Shillong Plateau act as a geometric asperity where interseismic strain may accumulate. Low-velocity anomalies in the lower crust probably play a major role to accommodating the stresses generated due to plate separation, culminating in future sources of great earthquakes. The geological faults are well imaged in the cross-sections and support the concept of Pop-up tectonics beneath the Shillong of NE India.

Identification of multiple underground explosions using the relative amplitude method

1988 ◽  
Vol 78 (2) ◽  
pp. 885-897
Author(s):  
R. A. Clark ◽  
R. G. Pearce
Keyword(s):  
Body Wave ◽  
The Body ◽  
P Wave ◽  
Relative Amplitude ◽  
Time Data ◽  
Large Measure ◽  
Source Discrimination ◽  
Nuclear Explosions ◽  
Short Period ◽  
Wave Forms

Abstract The relative amplitude method is applied to the few available good quality teleseismic P-wave seismograms from five presumed double nuclear explosions and one known multiple chemical explosion, under the “naive” assumption that the observed multiple arrivals correspond to P, pP, and sP from a single earthquake—an interpretation which is indeed consistent with the body-wave arrival time data in most cases. The purpose is to investigate the ability of relative amplitudes to identify correctly such multiple events for which established discrimination criteria may give earthquake-like or ambiguous results. For five of the examples, observed relative amplitudes from only four azimuthally well-distributed array seismograms are sufficient to exclude the single-earthquake interpretation. Deliberate attempts to simulate earthquake teleseismic P wave-forms using multiple explosions are restricted to simulation studies, and one of these is analyzed here using the same approach. We conclude that relative amplitudes can act as a valuable aid to source discrimination in cases where complexity gives rise to fallibility of conventional discriminants, even where only a small number of well-distributed teleseismic short-period array seismograms are available, their signal-to-noise ratios being maximized by suitable array design and careful choice of array site. The network need not be dense, since closely spaced observations of the focal sphere generally embody a large measure of redundancy.

scholarly journals IoT-enabled directed acyclic graph in spark cluster

2020 ◽  
Vol 9 (1) ◽  
Author(s):  
Jahwan Koo ◽  
Nawab Muhammad Faseeh Qureshi ◽  
Isma Farah Siddiqui ◽  
Asad Abbas ◽  
Ali Kashif Bashir
Keyword(s):  
Distributed Computing ◽  
Real Time ◽  
Directed Acyclic Graph ◽  
Random Access ◽  
Heterogeneous Data ◽  
The Body ◽  
Computing Environment ◽  
Time Data ◽  
Acyclic Graph ◽  
Sensory Data

Abstract Real-time data streaming fetches live sensory segments of the dataset in the heterogeneous distributed computing environment. This process assembles data chunks at a rapid encapsulation rate through a streaming technique that bundles sensor segments into multiple micro-batches and extracts into a repository, respectively. Recently, the acquisition process is enhanced with an additional feature of exchanging IoT devices’ dataset comprised of two components: (i) sensory data and (ii) metadata. The body of sensory data includes record information, and the metadata part consists of logs, heterogeneous events, and routing path tables to transmit micro-batch streams into the repository. Real-time acquisition procedure uses the Directed Acyclic Graph (DAG) to extract live query outcomes from in-place micro-batches through MapReduce stages and returns a result set. However, few bottlenecks affect the performance during the execution process, such as (i) homogeneous micro-batches formation only, (ii) complexity of dataset diversification, (iii) heterogeneous data tuples processing, and (iv) linear DAG workflow only. As a result, it produces huge processing latency and the additional cost of extracting event-enabled IoT datasets. Thus, the Spark cluster that processes Resilient Distributed Dataset (RDD) in a fast-pace using Random access memory (RAM) defies expected robustness in processing IoT streams in the distributed computing environment. This paper presents an IoT-enabled Directed Acyclic Graph (I-DAG) technique that labels micro-batches at the stage of building a stream event and arranges stream elements with event labels. In the next step, heterogeneous stream events are processed through the I-DAG workflow, which has non-linear DAG operation for extracting queries’ results in a Spark cluster. The performance evaluation shows that I-DAG resolves homogeneous IoT-enabled stream event issues and provides an effective stream event heterogeneous solution for IoT-enabled datasets in spark clusters.

The 4 December 2015 Mw 7.1 Normal-Faulting Antarctic Plate Earthquake and Its Seismotectonic Implications

2020 ◽  
Vol 110 (3) ◽  
pp. 1090-1100
Author(s):  
Ronia Andrews ◽  
Kusala Rajendran ◽  
N. Purnachandra Rao
Keyword(s):  
Body Wave ◽  
Focal Depth ◽  
Normal Fault ◽  
Normal Faults ◽  
Oceanic Plate ◽  
Normal Faulting ◽  
Transform Faults ◽  
Wave Inversion ◽  
Spreading Ridges ◽  
Southeast Indian Ridge

ABSTRACT Oceanic plate seismicity is generally dominated by normal and strike-slip faulting associated with active spreading ridges and transform faults. Fossil structural fabrics inherited from spreading ridges also host earthquakes. The Indian Oceanic plate, considered quite active seismically, has hosted earthquakes both on its active and fossil fault systems. The 4 December 2015 Mw 7.1 normal-faulting earthquake, located ∼700  km south of the southeast Indian ridge in the southern Indian Ocean, is a rarity due to its location away from the ridge, lack of association with any mapped faults and its focal depth close to the 800°C isotherm. We present results of teleseismic body-wave inversion that suggest that the earthquake occurred on a north-northwest–south-southeast-striking normal fault at a depth of 34 km. The rupture propagated at 2.7  km/s with compact slip over an area of 48×48  km2 around the hypocenter. Our analysis of the background tectonics suggests that our chosen fault plane is in the same direction as the mapped normal faults on the eastern flanks of the Kerguelen plateau. We propose that these buried normal faults, possibly the relics of the ancient rifting might have been reactivated, leading to the 2015 midplate earthquake.

Differences in the rupture process for very deep earthquakes at the Peru-Brazil and Peru-Bolivia borders 

2021 ◽  
Author(s):  
Elisa Buforn ◽  
Carmen Pro ◽  
Hernando Tavera ◽  
Agustin Udias ◽  
Maurizio Mattesini
Keyword(s):  
Focal Depth ◽  
Vertical Plane ◽  
Rupture Process ◽  
The South ◽  
Nazca Plate ◽  
Deep Earthquakes ◽  
Pressure Axis ◽  
Rate Functions ◽  
The Moment ◽  
Epicentral Location

<p>We analyze the differences in the rupture process for twelve very deep earthquakes (h>500 km) at the Peruvian-Brazilian subduction zone. These earthquakes are produced by the contact between the Nazca and the South America Plates. We have estimated the focal mechanism from teleseismic waveforms, using the slip inversion over the rupture plane, testing rupture velocities ranging from 2.5 km/s to 4.5 km/s, and analyzing the slip distribution for each  rupture velocity. The selected 12 earthquakes have occurred in the period 1994- 2016, with magnitudes between 5.9 and 8.2 and focal depth 500- 700 km. They can be separated in two groups attending to their epicentral location. The first group is formed by 9 events located, in the Peruvian-Brazil border, with epicenters following a NNW-SSE alignment, parallel to the trench. Their focal mechanisms present solutions of normal faulting with planes oriented in NS direction, dipping about 45 degrees and with vertical pressure axis. The second group is formed by three earthquakes located to the south of the first group in northern Bolivia. Their mechanisms show dip-slip motion with a near vertical plane, oriented in NW-SE direction and the pressure axis dipping 45º to the NE. The moment rate functions correspond to single ruptures with time durations from 6s to 12s, with the exception of the large 1994 Bolivian earthquake (Mw = 8.2) which presents a complex and longer STF. The different mechanisms for the two groups of earthquakes confirm the different dip of the subducting Nazca plate at the two areas, with the steeper part at the southern one.  </p>

Preliminary body-wave analysis of the St. Elias, Alaska earthquake of February 28, 1979

1980 ◽  
Vol 70 (2) ◽  
pp. 419-436
Author(s):  
John Boatwright
Keyword(s):  
New York ◽  
Body Wave ◽  
The Body ◽  
Rupture Velocity ◽  
Wave Analysis ◽  
S Waves ◽  
Initial Event ◽  
Whole Space ◽  
A New Technique ◽  
Alaska Earthquake

abstract Employing a new technique for the body-wave analysis of shallow-focus earthquakes, we have made a preliminary analysis of the St. Elias, Alaska earthquake of February 28, 1979, using five long-period P and S waves recorded at three WWSSN stations and at Palisades, New York. Using a well determined focal mechanism and an average source depth of ≈ 11 km, the interference of the depth phases (i.e., pP and sP, or sS) has been deconvolved from the recorded pulse shapes to obtain velocity and displacement pulse shapes as they would appear if the earthquake had occurred within an infinite medium. These “approximate whole space” pulse shapes indicate that the rupture contained three distinct subevents as well as a small initial event which preceded this subevent sequence by about 7 sec. From the pulse rise times of the subevents, their rupture lengths are estimated as 12, 27, and 17 km, assuming that the subevent rupture velocity was 3 km/sec. Overall, the earthquake ruptured ≈ 60 km to the southeast with an average rupture velocity of 2.2 km/sec. The cumulative body-wave moment for the whole event, 1.2 × 1027 dyne-cm, is substantially smaller than the surface-wave moments reported by Lahr et al. (1979) of 5 × 1027 dyne-cm. The moments of the subevents are estimated to be 0.6, 3.2, and 7.5 × 1026 dyne-cm, respectively.

Integrative taxonomic methods reveal an incorrect synonymisation of the South African Pseudonereis podocirra (Schmarda) as the widespread Pseudonereis variegata (Grube) from Chile

2018 ◽  
Vol 32 (6) ◽  
pp. 1282 ◽  
Author(s):  
Jyothi Kara ◽  
Angus H. H. Macdonald ◽  
Carol A. Simon
Keyword(s):  
South Africa ◽  
South African ◽  
Species Delimitation ◽  
Haplotype Network ◽  
The Body ◽  
General Description ◽  
The South ◽  
Morphological Examination ◽  
Genetic Structuring ◽  
The Status

The nereidid Pseudonereis variegata (Grube, 1866) described from Chile includes 14 synonymised species from 10 type localities with a discontinuous distribution, but no taxonomic or molecular studies have investigated the status of this species outside Chile. Two synonymised species, Mastigonereis podocirra Schmarda, 1861 and Nereis (Nereilepas) stimpsonis Grube, 1866, were described from South Africa and investigated here using morphological examination. MtCOI species delimitation analyses and morphology were used to determine the status of P. variegata in South Africa. Morphological examination revealed that museum and freshly collected specimens from South Africa that conform to the general description of P. variegata are similar to M. podocirra and N. stimpsonis with respect to the consistent absence of homogomph spinigers in the inferior neuropodial fascicle, expanded notopodial ligules and the subterminal attachment of dorsal cirri in posterior parapodia. The synonymy of M. podocirra and N. stimpsonis as P. variegata are rejected and P. podocirra, comb. nov. is reinstated. Morphologically, Pseudonereis podocirra differed from specimens from Chile with regard to the numbers of paragnaths, the absence of homogomph spinigers and changes in parapodial morphology along the body. Independence of these species was further supported by genetic distances, automatic barcode gap discovery and multi-rate Poisson tree process species delimitation analyses of 77 mtCOI sequences. Haplotype network revealed no genetic structuring within the South African populations. http://zoobank.org/urn:lsid:zoobank.org:pub:F0B1A5AF-9CE9-4A43-ACCF-17117E1C2F21

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