scholarly journals Large scale processing of seismic data in search of regional and global stress patterns

1968 ◽  
Vol 58 (6) ◽  
pp. 1899-1932
Author(s):  
A. Ben-Menahem ◽  
H. Jarosch ◽  
M. Rosenman
Keyword(s):  
Spectral Analysis ◽  
Surface Waves ◽  
Seismic Data ◽  
Large Scale ◽  
Focal Depth ◽  
Body Waves ◽  
Depth Range ◽  
Tsunami Warning System ◽  
Period Range ◽  
Stress Patterns

ABSTRACT A composite compute program has been devised for a fast reduction of multistation seismic data in the period range 50–500 sec for mantle surface waves and 20–100 sec for body waves. The analysis aims at the reconstruction of the seismic source from the spectrum of its far radiation field and the correlation of its parameters with its depth, size and regional environment. The capability of the computational procedure has been demonstated in two studies of WWNSS records: one includes a spectral analysis of surface waves from a shallow shock in the Kurile Islands; the other includes a spectral analysis of P waves from 9 shocks in the depth range 550–700 km at Fiji, Mariana, Java, Japan, Peru and Brazil. Other applications of the proposed data processing routine are foreseen; a tsunami warning system and focal depth determination from spectral modal ratios. It is believed that a persistent search for stress patterns, based on the processing of a sufficiently large sample of seismic events, is essential to any future program of earthquake prediction.

scholarly journals Long-period modelling of MEDNET waveforms for the December 13, 1990 Eastern Sicily earthquake

1995 ◽  
Vol 38 (2) ◽  
Author(s):  
D. Giardini ◽  
B. Palombo ◽  
N. A. Pino
Keyword(s):  
Surface Waves ◽  
Eastern Mediterranean ◽  
Broad Band ◽  
Low Noise ◽  
Body Waves ◽  
Digital Data ◽  
Depth Range ◽  
Period Range ◽  
Velocity Models ◽  
S Period

The availability of broad-band digital data allow "the analysis" of the seismic signal in the low-noise frequency band for structural and seismic source studies, We model complete seismograms -surface and body waves - for the December 13, 1 990, Eastern Sicily earthquake, recorded at regional distances on the MEDNET stations AQU, BNI and KEG, The inversion for the moment tensor is carried out following two approaches: a) a model-independent stralegy to fit complete seismograms in the 100-130 s period range; b) the calibration of phase velocity curves along each path to fit surface waves in the 40-100 s range, Both methodologies yield stable and consistent results: the 1990 Eastern Sicily earthquake had a seismic moment of M/o = 37 x 1024 dyne.cm, corresponding lo magnitude values of mb = 5,5, Ms = 5,7, Mw = ML = 5.8. In a second stage, synthetic seismograms arc generated by full reflectivity in the 5-50 s period range, with a new code based on the "minors" integration. By modelling surface waves in the 30-50 s range and body waves to 5 s periods, we derive average velocity models for the Central and Eastern Mediterranean, and constrain the hypocenter of the 1990 Eastern Sicily earthquake to be in the 13-17 km depth range.

Short-period seismic noise

1967 ◽  
Vol 57 (1) ◽  
pp. 55-81
Author(s):  
E. J. Douze
Keyword(s):  
Surface Waves ◽  
Rayleigh Waves ◽  
Seismic Noise ◽  
Body Waves ◽  
Deep Hole ◽  
Period Range ◽  
Short Period ◽  
The Subject ◽  
Hole Arrays

abstract This report consists of a summary of the studies conducted on the subject of short-period (6.0-0.3 sec period) noise over a period of approximately three years. Information from deep-hole and surface arrays was used in an attempt to determine the types of waves of which the noise is composed. The theoretical behavior of higher-mode Rayleigh waves and of body waves as measured by surface and deep-hole arrays is described. Both surface and body waves are shown to exist in the noise. Surface waves generally predominate at the longer periods (of the period range discussed) while body waves appear at the shorter periods at quiet sites. Not all the data could be interpreted to define the wave types present.

scholarly journals Bayesian inversion of the Martian structure using geodynamic constraints

2021 ◽  
Author(s):  
Mélanie Drilleau ◽  
Henri Samuel ◽  
Attilio Rivoldini ◽  
Mark Panning ◽  
Philippe Lognonné
Keyword(s):  
Surface Waves ◽  
Seismic Data ◽  
Epicentral Distance ◽  
Receiver Functions ◽  
Body Waves ◽  
Moho Depth ◽  
Model Parameters ◽  
Seismic Structure ◽  
Data Set ◽  
Single Station

Summary The ongoing InSight mission has recently deployed very broad band seismometers to record the Martian seismic activity. These recordings constitute the first seismic data set collected at the surface of Mars. This unique but sparse record compels for the development of new techniques tailored to make the best use of the specific context of single station-multiple events with several possible ranges of uncertainties on the event location. To this end, we conducted sets of Markov chain Monte-Carlo inversions for the 1-D seismic structure of Mars. We compared two inversion techniques that differ from the nature of the parameterization on which they rely. A first classical approach based on a parameterization of the 1-D seismic profile using Bézier curves. A second, less conventional approach that relies on a parameterization in terms of quantities that influence the thermo-chemical evolution of the planet (mantle rheology, initial thermal state, and composition), which accounts for 4.5 Gyr of planetary evolution. We considered several combinations of true model parameters to retrieve, and explored the influence of the type of seismic data (body waves with or without surface waves), the number of events and their associated epicentral distances and uncertainties, and the presence of potential constraints on Moho depth inferred from independent measurements/considerations (receiver functions and gravity data). We show that due to its inherent tighter constraints the coupled approach allows a considerably better retrieval of Moho depth and the seismic structure underneath it than the classical inversion, under the condition that the physical assumptions made in coupled approach are valid for Mars. In addition, our tests indicate that in order to constrain the seismic structure of Mars with InSight data, the following independent conditions must be met: (1) The presence of surface waves triggered by an internal source to constrain the epicentral distance. (2) The presence of just a few well-localized impact sources, with at least one located at close epicentral distance (<5○) to illuminate independently the crust and the mantle. In addition to providing tighter constraints of Mars seismic structure, geodynamically-constrained inversions allow one to reconstruct the thermo-chemical and rheological history of Mars until present. Therefore, even with a relatively small amount of large events and in absence of surface waves, constraining the present-day structure and long-term evolution of the red planet remains possible through the use of tailored hybrid inversion schemes.

scholarly journals Implementation of Machine Learning Algorithms in Spectral Analysis of Surface Waves (SASW) Inversion

2021 ◽  
Vol 11 (6) ◽  
pp. 2557
Author(s):  
Sadia Mannan Mitu ◽  
Norinah Abd. Rahman ◽  
Khairul Anuar Mohd Nayan ◽  
Mohd Asyraf Zulkifley ◽  
Sri Atmaja P. Rosyidi
Keyword(s):  
Spectral Analysis ◽  
Surface Waves ◽  
Soil Profile ◽  
Field Tests ◽  
Iteration Process ◽  
Machine Learning Algorithms ◽  
Support Vector ◽  
Complex Processes ◽  
Inversion Procedure ◽  
Inversion Analysis

One of the complex processes in spectral analysis of surface waves (SASW) data analysis is the inversion procedure. An initial soil profile needs to be assumed at the beginning of the inversion analysis, which involves calculating the theoretical dispersion curve. If the assumption of the starting soil profile model is not reasonably close, the iteration process might lead to nonconvergence or take too long to be converged. Automating the inversion procedure will allow us to evaluate the soil stiffness properties conveniently and rapidly by means of the SASW method. Multilayer perceptron (MLP), random forest (RF), support vector regression (SVR), and linear regression (LR) algorithms were implemented in order to automate the inversion. For this purpose, the dispersion curves obtained from 50 field tests were used as input data for all of the algorithms. The results illustrated that SVR algorithms could potentially be used to estimate the shear wave velocity of soil.

Line length balancing to evaluate multi-phase submarine landslide development: an example from the Storegga Slide, Norway

2019 ◽  
Vol 500 (1) ◽  
pp. 531-549 ◽  
Author(s):  
Suzanne Bull ◽  
Joseph A. Cartwright
Keyword(s):  
Seismic Data ◽  
Large Scale ◽  
Line Length ◽  
Proximal Region ◽  
Submarine Landslide ◽  
Landslide Development ◽  
Multi Phase ◽  
Storegga Slide ◽  
2D And 3D ◽  
3D Seismic Data

AbstractThis study shows how simple structural restoration of a discrete submarine landslide lobe can be applied to large-scale, multi-phase examples to identify different phases of slide-lobe development and evaluate their mode of emplacement. We present the most detailed analysis performed to date on a zone of intense contractional deformation, historically referred to as the compression zone, from the giant, multi-phase Storegga Slide, offshore Norway. 2D and 3D seismic data and bathymetry data show that the zone of large-scale (>650 m thick) contractional deformation can be genetically linked updip with a zone of intense depletion across a distance of 135 km. Quantification of depletion and accumulation along a representative dip-section reveals that significant depletion in the proximal region is not accommodated in the relatively mild amount (c. 5%) of downdip shortening. Dip-section restoration indicates a later, separate stage of deformation may have involved removal of a significant volume of material as part of the final stages of the Storegga Slide, as opposed to the minor volumes reported in previous studies.

Spectral analysis of surface waves for non-destructive evaluation of historic masonry buildings

2021 ◽  
Vol 52 ◽  
pp. 31-37
Author(s):  
Fernando Martínez-Soto ◽  
Fernando Ávila ◽  
Esther Puertas ◽  
Rafael Gallego
Keyword(s):  
Spectral Analysis ◽  
Surface Waves ◽  
Masonry Buildings ◽  
Historic Masonry ◽  
Non Destructive Evaluation ◽  
Non Destructive

Azimuthal multiple signal classification of dispersive and aliased surface waves recorded in 3D seismic acquisition

Geophysics ◽  
2021 ◽  
pp. 1-84
Author(s):  
Chunying Yang ◽  
Wenchuang Wang
Keyword(s):  
Surface Wave ◽  
Surface Waves ◽  
Body Waves ◽  
Signal Classification ◽  
Dispersion Pattern ◽  
Velocity Spectrum ◽  
Low Velocity ◽  
Surface Wave Dispersion ◽  
Multiple Signal Classification ◽  
Multiple Signal

Irregular acquisition geometry causes discontinuities in the appearance of surface wave events, and a large offset causes seismic records to appear as aliased surface waves. The conventional method of sampling data affects the accuracy of the dispersion spectrum and reduces the resolution of surface waves. At the same time, ”mode kissing” of the low-velocity layer and inhomogeneous scatterers requires a high-resolution method for calculating surface wave dispersion. This study tested the use of the multiple signal classification (MUSIC) algorithm in 3D multichannel and aliased wavefield separation. Azimuthal MUSIC is a useful method to estimate the phase velocity spectrum of aliased surface wave data, and it represent the dispersion spectra of low-velocity and inhomogeneous models. The results of this study demonstrate that mode-kissing affects dispersion imaging, and inhomogeneous scatterers change the direction of surface-wave propagation. Surface waves generated from the new propagation directions are also dispersive. The scattered surface wave has a new dispersion pattern different to that of the entire record. Diagonal loading was introduced to improve the robustness of azimuthal MUSIC, and numerical experiments demonstrate the resultant effectiveness of imaging aliasing surface waves. A phase-matched filter was applied to the results of azimuthal MUSIC, and phase iterations were unwrapped in a fast and stable manner. Aliased surface waves and body waves were separated during this process. Overall, field data demonstrate that azimuthal MUSIC and phase-matched filters can successfully separate aliased surface waves.

The rupture process and aftershock distribution of the 6 April 1992 MS 6.8 earthquake, Offshore British Columbia

1995 ◽  
Vol 85 (3) ◽  
pp. 716-735 ◽  
Author(s):  
John F. Cassidy ◽  
Garry C. Rogers
Keyword(s):  
Surface Waves ◽  
Triple Junction ◽  
Rupture Process ◽  
Body Waves ◽  
Ocean Bottom Seismometer ◽  
Strain Accumulation ◽  
Transform Fault ◽  
Junction Region ◽  
Long Period ◽  
Initial Rupture

Abstract On 6 April 1992, a magnitude 6.8 (MS) earthquake occurred in the triple-junction region at the northern end of the Cascadia subduction zone. This was the largest earthquake in at least 75 yr to occur along the 110-km-long Revere-Dellwood-Wilson (RDW) transform fault and the first large earthquake in this region recorded by modern broadband digital seismic networks. It thus provides an opportunity to examine the rupture process along a young (<2 Ma) oceanic transform fault and to gain better insight into the tectonics of this triple-junction region. We have investigated the source parameters and the rupture process of this earthquake by modeling broadband body waves and long-period surface waves and by accurately locating the mainshock and the first 10 days of aftershocks using a well-located “calibration” event recorded during an ocean-bottom seismometer survey. Analysis of P and SH waveforms reveals that this was a complex rupture sequence consisting of three strike-slip subevents in 12 sec. The initial rupture occurred 5 to 6 km to the SW of the seafloor trace of the RDW fault at 50.55° N, 130.46° W. The dominant subevent occurred 2 to 3 sec later and 4.3 km beneath the seafloor trace of the RDW fault, and a third subevent occurred 5 sec later, 18 km to the NNW, suggesting a northwestward propagating rupture. The aftershock sequence extended along a 60- to 70-km-long segment of the RDW fault, with the bulk of the activity concentrated ∼30 to 40 km to the NNW of the epicenter, consistent with this interpretation. The well-constrained mechanism of the initial rupture (strike/dip/slip 339°/90°/−168°) and of the largest aftershock (165°/80°/170°) are rotated 15° to 20° clockwise relative to the seafloor trace of the RDW fault but are parallel to the Pacific/North America relative plate motion vector. In contrast, the mechanisms of the dominant subevent (326°/87°/−172°), and the long-period solution derived from surface waves aligns with the RDW fault. This suggests that small earthquakes (M < 6) in this area occur along faults that are optimally aligned with respect to the regional stress field, whereas large earthquakes, involving tens of kilometers of rupture, activate the RDW fault. For the mainshock, we estimate a seismic moment (from surface waves) of 1.0 × 1026 dyne-cm, a stress drop of 60 bars, and an average slip of 1.2 m. This represents only 21 yr of strain accumulation, implying that there is either a significant amount of aseismic slip along the RDW fault or that much of the strain accumulation manifests itself as deformation within the Dellwood and Winona blocks or along the continental margin.

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