Estimation of earthquakes location errors distribution for LUMINEOS local seismic network in Poland. 

2021 ◽  
Author(s):  
Jakub Kokowski ◽  
Łukasz Rudziński
Keyword(s):  
Noise Level ◽  
Velocity Model ◽  
Seismic Network ◽  
Simple Task ◽  
Detection Range ◽  
S Waves ◽  
Location Errors ◽  
Precise Knowledge ◽  
Observation Network ◽  
Copper Mines

<p>Estimation of hypocenter location errors  is not a simple task. These errors are influenced by many factors. The most important are: the quality of velocity model, the configuration of stations in the observation network and the noise level recorded at stations. While the network configuration affects the error distribution in a deterministic manner, the noise level is largely random. It means that the uncertainties cannot be determined in a deterministic way and only statistical approach can be used. There are several methods for estimating location errors for particular seismic network. Some techniques use synthetic seismograms to calculate the detection range related to each station. However, this approach requires very precise knowledge of the geological model, which is not always possible. Instead, in this work we present a different approach, which uses only phase data for events included in the catalog. In this method, the detection range for each station is estimated using the detection probability (Schorlemmer & Woessner, 2008) used for both P- and S- waves first arrivals. The usefulness of this approach is discussed assuming the shape of  LUMINEOS seismic network which operates in the Legnica-Głogów Copper District (LGCD), Poland. In the LGCD region seismic activity is related to three deep underground copper mines. Every year thousand of seismic events with magnitudes up to M4.0 are registered here. Some of them are followed by tragic mining collapses and are widely felt by local residents.</p>

Scalar reverse‐time depth migration of prestack elastic seismic data

Geophysics ◽  
2001 ◽  
Vol 66 (5) ◽  
pp. 1519-1527 ◽  
Author(s):  
Robert Sun ◽  
George A. McMechan
Keyword(s):  
Seismic Waves ◽  
Velocity Model ◽  
P Wave ◽  
Common Source ◽  
Reverse Time ◽  
S Wave ◽  
Wave Source ◽  
Reflected Waves ◽  
S Waves ◽  
Elastic Data

Reflected P‐to‐P and P‐to‐S converted seismic waves in a two‐component elastic common‐source gather generated with a P‐wave source in a two‐dimensional model can be imaged by two independent scalar reverse‐time depth migrations. The inputs to migration are pure P‐ and S‐waves that are extracted by divergence and curl calculations during (shallow) extrapolation of the elastic data recorded at the earth’s surface. For both P‐to‐P and P‐to‐S converted reflected waves, the imaging time at each point is the P‐wave traveltime from the source to that point. The extracted P‐wave is reverse‐time extrapolated and imaged with a P‐velocity model, using a finite difference solution of the scalar wave equation. The extracted S‐wave is reverse‐time extrapolated and imaged similarly, but with an S‐velocity model. Converted S‐wave data requires a polarity correction prior to migration to ensure constructive interference between data from adjacent sources. Synthetic examples show that the algorithm gives satisfactory results for laterally inhomogeneous models.

Evaluation of the Detection and Location Capability of the Seismic Network in the Western Part of the North Caucasus Using Network Layout and Local Microseismic Noise Level

2021 ◽  
Vol 57 (2) ◽  
pp. 209-230
Author(s):  
A. A. Malovichko ◽  
I. P. Gabsatarova ◽  
R. A. Dyagilev ◽  
D. Yu. Mekhryushev ◽  
A. S. Zvereva
Keyword(s):  
Noise Level ◽  
Seismic Network ◽  
North Caucasus ◽  
The North ◽  
Network Layout

scholarly journals Seismic characterization of multiple fracture sets at Rulison Field, Colorado

Geophysics ◽  
2007 ◽  
Vol 72 (2) ◽  
pp. B19-B30 ◽  
Author(s):  
Ivan Vasconcelos ◽  
Vladimir Grechka
Keyword(s):  
Velocity Model ◽  
Multiple Fracture ◽  
Fracture Characterization ◽  
Seismic Reflection Data ◽  
Characterization Methods ◽  
S Waves ◽  
Reflection Data ◽  
Seismic Characterization ◽  
Inversion Procedure

Conventional fracture-characterization methods assume the presence of a single set of aligned, vertical cracks in the subsur-face. We relax this assumption and demonstrate the feasibility of seismic characterization of multiple fracture sets. Our technique relies on recent numerical findings indicating that multiple, differently oriented, possibly intersecting planar cracks embedded in an otherwise isotropic host rock result in a nearly orthorhombic (or orthotropic) effective medium. Here, the governing parameters of crack-induced orthotropy are estimated from 3D, wide-azimuth, multicomponent seismic reflection data acquired over the tight-gas Rulison Field in Colorado. We translate strong azimuthal variations of the normal-moveout velocities intointerval crack densities, fracture orientations, type of fluid infill, and velocities of P- and S-waves in an unfractured rock. Our inversion procedure identifies a set of cracks aligned in approximately west northwest-east southeast direction in the western part of the study area and multiple, likely intersecting fractures in its eastern part. We validate both our underlying theoretical model and the obtained estimates by two independent measurements: (1) the estimated fluid-infill parameter indicates dry cracks as expected for the gas-producing sandstones at Rulison; and (2) the obtained crack orientations are supported by well observations. As a by-product of fracture characterization, we build an anisotropic velocity model of the Rulison reservoir which, we believe, is the first orthorhombic velocity field constructed from surface seismic data.

Salt-flank delineation by interferometric imaging of transmitted P- to S-waves

Geophysics ◽  
2006 ◽  
Vol 71 (4) ◽  
pp. SI197-SI207 ◽  
Author(s):  
Xiang Xiao ◽  
Min Zhou ◽  
Gerard T. Schuster
Keyword(s):  
Velocity Model ◽  
Seismic Profile ◽  
Migration Velocity ◽  
Interferometric Imaging ◽  
S Waves ◽  
Time Migration ◽  
Transmitted Waves ◽  
Imaging Results ◽  
Vsp Data ◽  
Migration Method

We describe how vertical seismic profile (VSP) interferometric imaging of transmitted P-to-S (PS) waves can be used to delineate the flanks of salt bodies. Unlike traditional migration methods, interferometric PS imaging does not require the migration velocity model of the salt and/or upper sediments in order to image the salt flank. Synthetic elastic examples show that PS interferometric imaging can clearly delineate the upper and lower boundaries of a realistic salt-body model. Results also show that PS interferometric imaging is noticeably more accurate than conventional migration methods in the presence of static shifts and/or migration velocity errors. However, the illumination area of the PS transmitted waves is limited by the width of the shot and geophone aperture, which means wide shot offsets and deeper receiver wells are needed for comprehensive salt-flank imaging. Interferometric imaging results for VSP data from the Gulf of Mexico demonstrate its superiority over the traditional migration method. We also discuss other arrivals that can be used for interferometric imaging of salt flanks. For comparison, reduced-time migration results are presented, which are similar in quality to those obtained for interferometric imaging. We conclude that PS interferometric imaging of VSP data provides the geophysicist with a new tool by which salt flanks can be viewed from both above and below VSP geophone locations.

scholarly journals Updated determination of earthquake magnitudes at the Swiss Seismological Service

2020 ◽  
Author(s):  
Roman Racine ◽  
Carlo Cauzzi ◽  
John Clinton ◽  
Donat Fäh ◽  
Benjamin Edwards ◽  
...  
Keyword(s):  
Seismic Hazard ◽  
Source Region ◽  
Strong Motion ◽  
Velocity Model ◽  
Seismic Network ◽  
Event Processing ◽  
Waveform Data ◽  
Data Archiving ◽  
Short Period ◽  
Magnitude Determination

<p>The Swiss Seismological Service (SED; http://www.seismo.ethz.ch) at ETH Zürich is the federal agency in charge of monitoring earthquakes in Switzerland and neighboring areas, and for the assessment of seismic hazard and risk for the region. The SED seismic network largely relies on software and databases integrated in the SeisComP3 monitoring suite for waveform acquisition, automatic and manual event processing, event alerting, web infrastructure, data archiving and dissemination. Data from all digital seismic stations acquired by the SED over the last 30 years - broadband (presently ~230), strong-motion (~185), short-period (~65), permanent and temporary - are homogeneously integrated in the seismic network processing tools and products. Waveform data from the Swiss National Seismic Networks are openly available through the SED website and ORFEUS EIDA / Strong-Motion (http://orfeus-eu.org/data/) data gateways. The SED earthquake catalogue is publicly available through FDSN Event web services at  the SED (http://arclink.ethz.ch/fdsnws/event/1/). The Swiss seismic hazard maps are integrated in the EFEHR portal (http://www.efehr.org). The SED is updating its strategy for magnitude determination to make it fully consistent with the state-of-the-art in engineering seismology and seismic hazard studies in Switzerland, and to optimise the use of its dense seismic monitoring infrastructure. Among the planned changes are the: (a) adoption of a new ML relationship applicable in the near-source region at epicentral distances smaller than 15-20 km; (b) inclusion of ML station corrections based on empirically observed (de)amplification with respect to the Swiss reference rock velocity model and associated predictions; (c)  seamless computation of Mw based on spectral fitting of recorded FAS using a Swiss specific model. In this contribution we present and discuss the updated magnitude computations for a playback dataset of thousands of recorded earthquakes, and compare them with the current official estimates. We discuss the expected impacts of the new magnitude determination strategy on the SED event processing chain in SeisComP3, the SED catalogues and other seismological products. We welcome community feedback on our planned transition strategy.</p>

scholarly journals Comparison Study of Crustal Structure in Aceh Region based on Volcanic Arc System using Receiver Function Method

2021 ◽  
Vol 2110 (1) ◽  
pp. 012003
Author(s):  
R I Mahardiana ◽  
P Ariyanto ◽  
B Pranata ◽  
B S Prayitno
Keyword(s):  
Crustal Structure ◽  
Receiver Function ◽  
Velocity Model ◽  
Moho Depth ◽  
Comparison Study ◽  
Forward Modelling ◽  
Backarc Basin ◽  
Volcanic Arc ◽  
S Waves ◽  
Receiver Function Method

Abstract Aceh region has a very complex crustal structure from the forearc ridge to the backarc basin. This study aims to determine the velocity model of P and S waves and the depth of Moho discontinuity. This research was conducted using teleseismic earthquake data (30°-90° from the station) with M>6 from four seismic stations belonging to the BMKG in Aceh region. The stations are qualified based on the volcanic arc system zone. Furthermore, the velocity model determined by result of forward modelling, while the depth of the Moho layer estimated by migrated receiver function from time domain to the depth domain. At station SNSI that represented the forearc ridge zone, the depth of Moho is ±28 km, at station TPTI represent the forearc basin is ±16 km, while at zone with higher topography, namely volcanic arc zone represented by station KCSI, the Moho depth was identified at ±38 km, and the backarc basin represented by station LASI with ±40 km depth of Moho. This variation occurs because the composition of the earth’s layers below the station is diverse also different topography for each station.

scholarly journals The May 7 - 11, 2016 Earthquake Sequence at Rivera Fault Zone

2020 ◽  
Author(s):  
Francisco J Nunez-Cornu ◽  
Diego Cordoba ◽  
William L Bandy ◽  
Juan José Dañobeitia ◽  
Carlos Mortera-Gutierrez ◽  
...  
Keyword(s):  
Pressure Sensors ◽  
Velocity Model ◽  
Tectonic Stress ◽  
Seismic Network ◽  
P Wave ◽  
Earthquake Sequence ◽  
Ocean Bottom ◽  
Transform Fault ◽  
Stress Regime ◽  
Short Period

<p>The geodynamic complexity in the interaction between Rivera, Cocos and NOAM plates is mainly reflected in the high and not well located seismicity of the region. In the framework of TsuJal Project, a study of the passive seismic activity was carried out. A temporal seismic network with 25 Obsidian stations with sensor Le-3D MkIII were deploying from the northern part of Nayarit state to the south of Colima state, including the Marias Islands, in addition to the Jalisco telemetric Seismic Network, being a total of 50 seismic stations on land. Offshore, ten Ocean Bottom Seismographs type LCHEAPO 2000 with 4 channels (3 seismic short period and 1 pressure sensors) were deployed and recover by the BO El Puma from UNAM in an array from the Marias Islands to off coast of the border of Colima and Michoacan state, in the period from 19th April to 7th November 2016.</p><p>A seismic sequence started on May 7, 2016 with an earthquake Mw = 5.6 reported by CMT-Harvard, USGS and SSN at the area north of Paleo Rivera Transform fault and west of the Middle America Trench, an area with a very complex tectonics due to the interaction of Rivera, Cocos and NOAM plates.</p><p>An analysis of this earthquake sequence from May 7 to May 11 using data from OBS and adequate P-Wave velocity model for Rivera plate is presented, 87 earthquakes were located. Data from onland stations were integrated after a travel-time residual analysis.</p><p>We observed that the new location is about 50 km southwest direction, from previous one, between the Paleo Rivera Transform fault and the northern tip of the East Pacific Rise – Pacific Cocos Segment.  This area has a different tectonic stress regime.</p>

Sign in / Sign up

Export Citation Format

Share Document