Self-consistent retrieval of source parameters using mantle waves

1998 ◽  
Vol 88 (4) ◽  
pp. 995-1002
Author(s):  
Karine Gouget ◽  
Pierre F. Ihmlé ◽  
Jaime Campos ◽  
Jean-Paul Montagner
Keyword(s):  
Spectral Synthesis ◽  
Source Parameters ◽  
Low Frequency ◽  
Large Earthquake ◽  
Time Function ◽  
Inversion Method ◽  
Global Networks ◽  
Self Consistent ◽  
Routine Basis ◽  
Narrow Frequency Band

Abstract The large number of high-quality stations from global networks (e.g., IRIS, GEOSCOPE) allows for rapid and robust recovery of source parameters of large earthquakes. We present a self-consistent analysis of surface waves in terms of directivity parameters. The boxcar is often used to recover source parameters but is rarely a faithful representation of an event's time function. We demonstrate that more reliable estimates of directivity parameters can be obtained when we take into account the source time function (STF) of the event. A low-frequency STF is obtained from first (R1) and second (R2) orbit Rayleigh waves in the range 2 to 15 mHz, with a spectral synthesis and inversion method. We measure the differential amplitudes between data and 3D synthetics. We use the R1/R2 ratio of differential amplitudes to invert, in a single narrow-frequency band, for the event's apparent rupture azimuth and velocity. For the Mw 8.1 Chile 1995 event, data are consistent with unilateral southward propagation, with a velocity of about 2.4 km/sec. For the Mw 7.9 Mexico 1995 earthquake, the rupture propagated toward the NW at about 2.0 km/sec. Our low-frequency estimates agree with broadband studies of both events and can be retrieved rapidly on a routine basis after a large earthquake.

scholarly journals Rapid Estimation of Earthquake Magnitude and Source Parameters Using Genetic Algorithms

2021 ◽  
Vol 11 (24) ◽  
pp. 11852
Author(s):  
Astri Novianty ◽  
Irwan Meilano ◽  
Carmadi Machbub ◽  
Sri Widiyantoro ◽  
Susilo Susilo
Keyword(s):  
Time Series ◽  
Genetic Algorithms ◽  
Early Warning ◽  
Time Series Data ◽  
Source Parameters ◽  
Large Earthquake ◽  
Series Data ◽  
Inversion Method ◽  
Permanent Displacement ◽  
Gps Time Series

To minimize the impacts of large losses and optimize the emergency response when a large earthquake occurs, an accurate early warning of an earthquake or tsunami is crucial. One important parameter that can provide an accurate early warning is the earthquake’s magnitude. This study proposes a method for estimating the magnitude, and some of the source parameters, of an earthquake using genetic algorithms (GAs). In this study, GAs were used to perform an inversion of Okada’s model from earthquake displacement data. In the first stage of the experiment, the GA was used to inverse the displacement calculated from the forward calculation in Okada’s model. The best performance of the GA was obtained by tuning the hyperparameters to obtain the most functional configuration. In the second stage, the inversion method was tested on GPS time series data from the 2011 Tohoku Oki earthquake. The earthquake’s displacement was first estimated from GPS time series data using a detection and estimation formula from previous research to calculate the permanent displacement value. The proposed method can estimate an earthquake’s magnitude and four source parameters (i.e., length, width, rake, and slip) close to the real values with reasonable accuracy.

Volume source-based extended waveform inversion

Geophysics ◽  
2018 ◽  
Vol 83 (5) ◽  
pp. R369-R387 ◽  
Author(s):  
Guanghui Huang ◽  
Rami Nammour ◽  
William W. Symes
Keyword(s):  
Penalty Function ◽  
Source Parameters ◽  
Waveform Inversion ◽  
Low Frequency ◽  
Model Space ◽  
Velocity Model ◽  
Inversion Method ◽  
Inversion Algorithm ◽  
Full Waveform ◽  
Data Frequency

Full-waveform inversion (FWI) faces the persistent challenge of cycle skipping, which can result in stagnation of the iterative methods at uninformative models with poor data fit. Extended reformulations of FWI avoid cycle skipping through adding auxiliary parameters to the model so that a good data fit can be maintained throughout the inversion process. The volume-based matched source waveform inversion algorithm introduces source parameters by relaxing the location constraint of source energy: It is permitted to spread in space, while being strictly localized at time [Formula: see text]. The extent of source energy spread is penalized by weighting the source energy with distance from the survey source location. For transmission data geometry (crosswell, diving wave, etc.) and transparent (nonreflecting) acoustic models, this penalty function is stable with respect to the data-frequency content, unlike the standard FWI objective. We conjecture that the penalty function is actually convex over much larger region in model space than is the FWI objective. Several synthetic examples support this conjecture and suggest that the theoretical limitation to pure transmission is not necessary: The inversion method can converge to a solution of the inverse problem in the absence of low-frequency data from an inaccurate initial velocity model even when reflections and refractions are present in the data along with transmitted energy.

scholarly journals Imaging the subsurface using induced seismicity and ambient noise: 3-D tomographic Monte Carlo joint inversion of earthquake body wave traveltimes and surface wave dispersion

2020 ◽  
Vol 222 (3) ◽  
pp. 1639-1655
Author(s):  
Xin Zhang ◽  
Corinna Roy ◽  
Andrew Curtis ◽  
Andy Nowacki ◽  
Brian Baptie
Keyword(s):  
Surface Wave ◽  
Ambient Noise ◽  
Velocity Structure ◽  
Joint Inversion ◽  
Body Wave ◽  
Source Parameters ◽  
Wave Dispersion ◽  
Inversion Method ◽  
Surface Wave Dispersion ◽  
Wave Data

SUMMARY Seismic body wave traveltime tomography and surface wave dispersion tomography have been used widely to characterize earthquakes and to study the subsurface structure of the Earth. Since these types of problem are often significantly non-linear and have non-unique solutions, Markov chain Monte Carlo methods have been used to find probabilistic solutions. Body and surface wave data are usually inverted separately to produce independent velocity models. However, body wave tomography is generally sensitive to structure around the subvolume in which earthquakes occur and produces limited resolution in the shallower Earth, whereas surface wave tomography is often sensitive to shallower structure. To better estimate subsurface properties, we therefore jointly invert for the seismic velocity structure and earthquake locations using body and surface wave data simultaneously. We apply the new joint inversion method to a mining site in the United Kingdom at which induced seismicity occurred and was recorded on a small local network of stations, and where ambient noise recordings are available from the same stations. The ambient noise is processed to obtain inter-receiver surface wave dispersion measurements which are inverted jointly with body wave arrival times from local earthquakes. The results show that by using both types of data, the earthquake source parameters and the velocity structure can be better constrained than in independent inversions. To further understand and interpret the results, we conduct synthetic tests to compare the results from body wave inversion and joint inversion. The results show that trade-offs between source parameters and velocities appear to bias results if only body wave data are used, but this issue is largely resolved by using the joint inversion method. Thus the use of ambient seismic noise and our fully non-linear inversion provides a valuable, improved method to image the subsurface velocity and seismicity.

scholarly journals Fully probabilistic seismic source inversion – Part 1: Efficient parameterisation

2013 ◽  
Vol 5 (2) ◽  
pp. 1125-1162 ◽  
Author(s):  
S. C. Stähler ◽  
K. Sigloch
Keyword(s):  
Moment Tensor ◽  
Source Parameters ◽  
Practical Importance ◽  
Principal Component ◽  
Seismic Source ◽  
Empirical Orthogonal Functions ◽  
Time Function ◽  
Source Inversion ◽  
Source Time Function ◽  
Earthquake Parameters

Abstract. Seismic source inversion is a non-linear problem in seismology where not just the earthquake parameters themselves, but also estimates of their uncertainties are of great practical importance. Probabilistic source inversion (Bayesian inference) is very adapted to this challenge, provided that the parameter space can be chosen small enough to make Bayesian sampling computationally feasible. We propose a framework for PRobabilistic Inference of Source Mechanisms (PRISM) that parameterises and samples earthquake depth, moment tensor, and source time function efficiently by using information from previous non-Bayesian inversions. The source time function is expressed as a weighted sum of a small number of empirical orthogonal functions, which were derived from a catalogue of >1000 STFs by a principal component analysis. We use a likelihood model based on the cross-correlation misfit between observed and predicted waveforms. The resulting ensemble of solutions provides full uncertainty and covariance information for the source parameters, and permits to propagate these source uncertainties into travel time estimates used for seismic tomography. The computational effort is such that routine, global estimation of earthquake mechanisms and source time functions from teleseismic broadband waveforms is feasible.

Study on bearing structure and joint seismic resistance of large span non-landing arch on high-speed railway station

2019 ◽  
Author(s):  
Liu Chuanping ◽  
Tianluan Liu ◽  
Jian Jia
Keyword(s):  
High Speed ◽  
Low Frequency ◽  
Large Earthquake ◽  
Scale Model ◽  
Railway Station ◽  
High Speed Railway ◽  
Long Span ◽  
Weak Component ◽  
Double Beam ◽  
Cyclic Loading Tests

<p>The main entrance of Chongqing West Railway Station adopts the non-landing compound arch with a span of 108m. In this paper, the nonlinear finite element theory is applied to analyze the bearing capacity and seismic ductility of the compound arch joints. Low frequency cyclic loading tests are performed on the 1/5 scale model. Based on the calculation and test results, a double beam structure and a section of steel truss are placed in the arch joints to bear the force of the arch. Moreover, the buckling-restrained brace (BRB) is placed in the lower part of the arch that enables most force directly transmit to the foundation of the arch. Unlike BRB’s common use as an inter-column support, it now acts as a buckling constraint support in the large earthquake. For instance, it can be yielded before the frame column to improve earthquake resistance. The research results indicate that the compound arch joint structure successfully accomplishes the seismic design goals of strong joints with weak component. Moreover, the study provides the theoretical basis and design reference for the application of BRB and long-span arch structures in high-speed railway station.</p>

scholarly journals Changes in the ultra-low frequency wave field during the precursor phase to the Sichuan earthquake: DEMETER observations

2013 ◽  
Vol 31 (9) ◽  
pp. 1597-1603 ◽  
Author(s):  
S. N. Walker ◽  
V. Kadirkamanathan ◽  
O. A. Pokhotelov
Keyword(s):  
Low Frequency ◽  
Large Earthquake ◽  
Short Term ◽  
Frequency Wave ◽  
Sichuan Earthquake ◽  
Ulf Wave ◽  
Precursor Phase ◽  
Demeter Satellite ◽  
Short Term Prediction ◽  
Atmospheric Gravity

Abstract. Electromagnetic phenomena observed in association with increases in seismic activity have been studied for several decades. These phenomena are generated during the precursory phases of an earthquake as well as during the main event. Their occurrence during the precursory phases may be used in short-term prediction of a large earthquake. In this paper, we examine ultra-low frequency (ULF) electric field data from the DEMETER satellite during the period leading up to the Sichuan earthquake. It is shown that there is an increase in ULF wave activity observed as DEMETER passes in the vicinity of the earthquake epicentre. This increase is most obvious at lower frequencies. Examination of the ULF spectra shows the possible occurrence of geomagnetic pearl pulsations, resulting from the passage of atmospheric gravity waves generated in the vicinity of the earthquake epicentre.

scholarly journals Calculation of a self-consistent, low frequency electrostatic field in toroidal geometry

1977 ◽  
Author(s):  
C. O. Beasley ◽  
H. K. Meier ◽  
W. I. van Rij ◽  
J. E. McCune
Keyword(s):  
Electrostatic Field ◽  
Low Frequency ◽  
Self Consistent ◽  
Toroidal Geometry

scholarly journals Комбинационное рассеяние света в хирально чистых и рацемической фазах поликристаллов триптофана и тирозина

2019 ◽  
Vol 127 (10) ◽  
pp. 541
Author(s):  
В.С. Горелик ◽  
М.Ф. Умаров ◽  
Ю.П. Войнов
Keyword(s):  
Amino Acids ◽  
Amino Acid ◽  
Raman Spectra ◽  
Spectral Range ◽  
Phase State ◽  
Source Parameters ◽  
Low Frequency ◽  
Aromatic Amino Acids ◽  
Chiral Phase ◽  
Left Handed

AbstractRaman spectra of tryptophan and tyrosine polycrystals have been analyzed in a wide spectral range by fiber-optic spectroscopy. The Raman spectra have been recorded with a BWS465-785H spectrometer in the spectral range of 0–2700 cm^–1 using a 785-nm cw laser as an excitation source. Parameters of the Raman spectra are compared for three crystalline phase modifications of aromatic amino acids: left-handed, right-handed, and racemic phase. The presence of strong Raman satellites, the characteristics of which change depending on the type of the chiral phase state of amino acid, is found in the low-frequency Raman spectra of tryptophan and tyrosine amino acid lattices. The results obtained can be used for monitoring the chiral purity of bioactive preparations containing amino acids.

Source-independent extended waveform inversion based on space-time source extension: Frequency-domain implementation

Geophysics ◽  
2018 ◽  
Vol 83 (5) ◽  
pp. R449-R461 ◽  
Author(s):  
Guanghui Huang ◽  
Rami Nammour ◽  
William W. Symes
Keyword(s):  
Source Function ◽  
Random Noise ◽  
A Priori ◽  
Waveform Inversion ◽  
Low Frequency ◽  
Inversion Method ◽  
Target Velocity ◽  
Extended Source ◽  
Full Waveform ◽  
Time Variables

Source signature estimation from seismic data is a crucial ingredient for successful application of seismic migration and full-waveform inversion (FWI). If the starting velocity deviates from the target velocity, FWI method with on-the-fly source estimation may fail due to the cycle-skipping problem. We have developed a source-based extended waveform inversion method, by introducing additional parameters in the source function, to solve the FWI problem without the source signature as a priori. Specifically, we allow the point source function to be dependent on spatial and time variables. In this way, we can easily construct an extended source function to fit the recorded data by solving a source matching subproblem; hence, it is less prone to cycle skipping. A novel source focusing annihilator, defined as the distance function from the real source position, is used for penalizing the defocused energy in the extended source function. A close data fit avoiding the cycle-skipping problem effectively makes the new method less likely to suffer from local minima, which does not require extreme low-frequency signals in the data. Numerical experiments confirm that our method can mitigate cycle skipping in FWI and is robust against random noise.

Regional propagation characteristics and source parameters of earthquakes in northeastern North America

1994 ◽  
Vol 84 (1) ◽  
pp. 1-15 ◽  
Author(s):  
John Boatwright
Keyword(s):  
Site Response ◽  
Source Parameters ◽  
Low Frequency ◽  
Response Spectra ◽  
Spectral Shape ◽  
Propagation Characteristics ◽  
S Wave ◽  
Data Set ◽  
Wave Trains ◽  
Source Site

Abstract The vertical components of the S wave trains recorded on the Eastern Canadian Telemetered Network (ECTN) from 1980 through 1990 have been spectrally analyzed for source, site, and propagation characteristics. The data set comprises some 1033 recordings of 97 earthquakes whose magnitudes range from M ≈ 3 to 6. The epicentral distances range from 15 to 1000 km, with most of the data set recorded at distances from 200 to 800 km. The recorded S wave trains contain the phases S, SmS, Sn, and Lg and are sampled using windows that increase with distance; the acceleration spectra were analyzed from 1.0 to 10 Hz. To separate the source, site, and propagation characteristics, an inversion for the earthquake corner frequencies, low-frequency levels, and average attenuation parameters is alternated with a regression of residuals onto the set of stations and a grid of 14 distances ranging from 25 to 1000 km. The iteration between these two parts of the inversion converges in about 60 steps. The average attenuation parameters obtained from the inversion were Q = 1997 ± 10 and γ = 0.998 ± 0.003. The most pronounced variation from this average attenuation is a marked deamplification of more than a factor of 2 at 63 km and 2 Hz, which shallows with increasing frequency and increasing distance out to 200 km. The site-response spectra obtained for the ECTN stations are generally flat. The source spectral shape assumed in this inversion provides an adequate spectral model for the smaller events (Mo &lt; 3 × 1021 dyne-cm) in the data set, whose Brune stress drops range from 5 to 150 bars. For the five events in the data set with Mo ≧ 1023 dyne-cm, however, the source spectra obtained by regressing the residuals suggest that an ω2 spectrum is an inadequate model for the spectral shape. In particular, the corner frequencies for most of these large events appear to be split, so that the spectra exhibit an intermediate behavior (where |ü(ω)| is roughly proportional to ω).

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