A waveform correlation method for identifying quarry explosions

1991 ◽  
Vol 81 (6) ◽  
pp. 2395-2418
Author(s):  
D. B. Harris
Keyword(s):  
Linear Combination ◽  
Correlation Method ◽  
P Wave ◽  
Large Signal ◽  
Source Regions ◽  
Single Station ◽  
Using Data ◽  
Element Array ◽  
Test Ban ◽  
Master Event

Abstract A waveform correlation method is presented for identifying quarry explosions by attributing them to known mines characterized by multiple master events. The objective is to provide a reliable automatic procedure for screening the large number of quarry explosions likely to be detected by networks of in-country stations monitoring compliance with test-ban treaties. The method generalizes existing correlation techniques to compare waveforms from an unlocated event recorded at an array of sensors with a linear combination of master event waveforms recorded at the same array. The use of a linear combination reduces the chance of a missed location caused by some variation in mechanism or spectral excitation between the events being compared. The weights in the linear combination are filters, offering some compensation for variations in source time functions and errors of waveform alignment. The use of array data reduces the likelihood of false attribution by reducing bias and variance in the correlation measurement. In a test conducted with P-wave data segments recorded at a 13-element array, the method successfully resolves two source regions separated by 4 km at a range of 150 km. Resolution with single-station waveform correlations is marginal due to the limited amount of data. The statistics of the sample waveform correlation coefficient are developed and demonstrate that single-station waveform correlations are unreliable unless estimated with large signal durations T or bandwidths B. A time-bandwidth TB product exceeding 100 (or smaller TB with more stations) is necessary for reliable event attribution. The related problem of separating superimposed waveforms from two events in different source regions may be solved by cancellation. The waveforms of one event are again approximated by a linear combination of waveforms from master events in the same mine. The residual signals, obtained by subtracting the approximation from the superimposed waveforms, estimate the waveforms from the second event. This method achieves significant separation of waveforms from events 6 km apart at a range of 150 km, using data from the 13-element array. Its resolution exceeds that of conventional beam-forming methods.

scholarly journals Relocation of clustered earthquakes in the Groningen gas field

2017 ◽  
Vol 96 (5) ◽  
pp. s163-s173 ◽  
Author(s):  
Lisanne Jagt ◽  
Elmer Ruigrok ◽  
Hanneke Paulssen
Keyword(s):  
S Wave ◽  
Gas Field ◽  
Single Station ◽  
Source Mechanisms ◽  
The Difference ◽  
Multiplet Analysis ◽  
Using Data ◽  
Groningen Gas Field ◽  
Master Event ◽  
Improved Accuracy

AbstractPrevious locations of earthquakes induced by depletion of the Groningen gas field were not accurate enough to infer which faults in the reservoir are reactivated. A multiplet analysis is performed to identify clusters of earthquakes that have similar waveforms, representing repeating rupture on the same or nearby faults. The multiplet analysis is based on the cross-correlation of seismograms to assess the degree of similarity. Using data of a single station, six earthquake clusters within the limits of the Groningen field were identified for the period 2010 to mid-2014. Four of these clusters were suitable for a relocation method that is based on the difference in travel time between the P- and the S-wave. Events within a cluster can be relocated relative to a master event with improved accuracy by cross-correlating first arrivals. By choosing master events located with a new dense seismic network, the relocated events likely not only have better relative, but also improved absolute locations. For a few clusters with sufficient signal-to-noise detections, we show that the relocation method is successful in assigning clusters to specific faults at the reservoir level. Overall, about 90% of the events did not show clustering, despite choosing low correlation thresholds of 0.5 and 0.6. This suggests that different faults and/or fault segments with likely varying source mechanisms are active in reservoir sub-regions of a few square kilometres.

Measurements of Rayleigh-wave phase velocities in Nevada: Implications for explosion sources and the Massachusetts Mountain earthquake

1982 ◽  
Vol 72 (4) ◽  
pp. 1329-1349
Author(s):  
H. J. Patton
Keyword(s):  
Rayleigh Wave ◽  
Rayleigh Waves ◽  
Moment Tensor ◽  
Test Site ◽  
P Wave ◽  
Stress Axis ◽  
Phase Velocities ◽  
Wave Phase ◽  
Single Station ◽  
Source Phase

abstract Single-station measurements of Rayleigh-wave phase velocity are obtained for paths between the Nevada Test Site and the Livermore broadband regional stations. Nuclear underground explosions detonated in Yucca Valley were the sources of the Rayleigh waves. The source phase φs required by the single-station method is calculated for an explosion source by assuming a spherically symmetric point source with step-function time dependence. The phase velocities are used to analyze the Rayleigh waves of the Massachusetts Mountain earthquake of 5 August 1971. Measured values of source phase for this earthquake are consistent with the focal mechanism determined from P-wave first-motion data (Fischer et al., 1972). A moment-tensor inversion of the Rayleigh-wave spectra for a 3-km-deep source gives a horizontal, least-compressive stress axis oriented N63°W and a seismic moment of 5.5 × 1022 dyne-cm. The general agreement between the results of the P-wave study of Fischer et al. (1972) and this study supports the measurements of phase velocities and, in turn, the explosion source model used to calculate φs.

Multiple geophysical investigations to characterize massive slope failure deposits: application to the Balta rockslide, Carpathians

2021 ◽  
Vol 225 (2) ◽  
pp. 1032-1047
Author(s):  
A-S Mreyen ◽  
L Cauchie ◽  
M Micu ◽  
A Onaca ◽  
H-B Havenith
Keyword(s):  
Surface Wave ◽  
Ambient Noise ◽  
Slope Failure ◽  
Seismic Refraction ◽  
P Wave ◽  
Surface Wave Dispersion ◽  
Seismic Region ◽  
Valley Bottom ◽  
Single Station ◽  
Landslide Body

SUMMARY Origins of ancient rockslides in seismic regions can be controversial and must not necessarily be seismic. Certain slope morphologies hint at a possible coseismic development, though further analyses are required to better comprehend their failure history, such as modelling the slope in its pre-failure state and failure development in static and dynamic conditions. To this effect, a geophysical characterization of the landslide body is crucial to estimate the possible failure history of the slope. The Balta rockslide analysed in this paper is located in the seismic region of Vrancea-Buzau, Romanian Carpathian Mountains and presents a deep detachment scarp as well as a massive body of landslide deposits. We applied several geophysical techniques on the landslide body, as well as on the mountain crest above the detachment scarp, in order to characterize the fractured rock material as well as the dimension of failure. Electrical resistivity measurements revealed a possible trend of increasing fragmentation of rockslide material towards the valley bottom, accompanied by increasing soil moisture. Several seismic refraction surveys were performed on the deposits and analysed in form of P-wave refraction tomographies as well as surface waves, allowing to quantify elastic parameters of rock. In addition, a seismic array was installed close to the detachment scarp to analyse the surface wave dispersion properties from seismic ambient noise; the latter was analysed together with a colocated active surface wave analysis survey. Single-station ambient noise measurements completed all over the slope and deposits were used to further reveal impedance contrasts of the fragmented material over in situ rock, representing an important parameter to estimate the depth of the shearing horizon at several locations of the study area. The combined methods allowed the detection of a profound contrast of 70–90 m, supposedly associated with the maximum landslide material thickness. The entirety of geophysical results was used as basis to build up a geomodel of the rockslide, allowing to estimate the geometry and volume of the failed mass, that is, approximately 28.5–33.5 million m3.

Source parameter determination of local earthquakes in Korea using moment tensor inversion of single station data

1999 ◽  
Vol 89 (4) ◽  
pp. 1077-1082 ◽  
Author(s):  
So Gu Kim ◽  
Nadeja Kraeva
Keyword(s):  
Moment Tensor ◽  
Source Parameters ◽  
Moment Tensor Inversion ◽  
P Wave ◽  
Parameter Determination ◽  
Reverse Fault ◽  
3D Tomography ◽  
Single Station ◽  
Slip Event

Abstract The purpose of this investigation is to determine source parameters such as focal mechanism, seismic moment, moment magnitude, and source depth from recent small earthquakes in the Korcan Peninsula using broadband records of three-component single station. It is very important and worthwhile to use a three-component single station in Korea because for most Korean earthquakes it is not possible to read enough first motions of P-wave arrivals because of the poor coverage of the seismic network and the small size (ML 5.0 or less) of the events. Furthermore the recent installation of the very broadband seismic stations in Korea and use of a 3D tomography technique can enhance moment tensor inversion to determine the source parameters of small earthquakes (ML 5.0 or less) that occur at near-regional distances (Δ ≤ 500 km). The focal solution for the Youngwol earthquake of 13 December 1996 is found to be a right-lateral strike slip event with a NE strike, and the Kyongju earthquake of 25 June 1997 is found to be an oblique reverse fault with a slight component of left-lateral slip in the SE direction.

WIDE‐BAND EXTRACTION OF MANTLE P WAVES FROM AMBIENT NOISE

Geophysics ◽  
1964 ◽  
Vol 29 (5) ◽  
pp. 672-692 ◽  
Author(s):  
Milo Backus ◽  
John Burg ◽  
Dick Baldwin ◽  
Ed Bryan
Keyword(s):  
Ambient Noise ◽  
Wide Band ◽  
P Wave ◽  
Cumberland Plateau ◽  
P Waves ◽  
Single Output ◽  
Short Period ◽  
Multichannel Filtering ◽  
On Line ◽  
Element Array

The spatial correlation characteristics of ambient short‐period (0.5 to 5 cps) noise at Ft. Sill, Oklahoma, and on the Cumberland Plateau in Tennessee were investigated on “permanent” arrays with 3–4 kilometer diameter. Dominant ambient noise at the two locations is spatially organized, and to first order may be treated as a combination of seismic propagating wave trains. At the Tennessee location noise energy above one cps is dominantly propagating with velocities from 3.5 to 4.5 km/sec, and must be carried in deeply trapped, high‐order modes. Generalized multichannel filtering (Burg) can be used to preserve a large class of mantle P‐wave signals, wide‐band, in a single output trace, while at the same time specifically rejecting ambient noise on the basis of its organization. Results of generalized multichannel filtering applied on‐line at the nineteen‐element array in Tennessee and applied off‐line are discussed.

P-wave fracture prediction algorithm using data with limited azimuthal distribution

2012 ◽  
Vol 31 (2) ◽  
pp. 198-205 ◽  
Author(s):  
Sam Zandong Sun ◽  
Xi Xiao ◽  
Lei Chen ◽  
Pei Yang ◽  
Haijun Yang ◽  
...  
Keyword(s):  
Fracture Prediction ◽  
P Wave ◽  
Prediction Algorithm ◽  
Azimuthal Distribution ◽  
Using Data

Toward Simultaneous Determination of Bulk Crustal Properties Using Virtual Deep Seismic Sounding

2020 ◽  
Vol 110 (3) ◽  
pp. 1387-1392 ◽  
Author(s):  
Qing Chen ◽  
Wang-Ping Chen
Keyword(s):  
Wave Train ◽  
Silica Content ◽  
P Wave ◽  
Deep Seismic Sounding ◽  
Wide Angle ◽  
Virtual Source ◽  
S Wave ◽  
Large Signal ◽  
Seismic Sounding ◽  
Central Tibet

ABSTRACT We augment the method of virtual deep seismic sounding (VDSS) by adding the phases Sp, the SV-P conversion across the Moho, to determine the average speed of the S wave (VS) in the crust. VDSS uses the strong SV-P conversion below the free surface from teleseismic earthquakes as a virtual source for wide-angle reflections of the P wave. The large signal generated by the virtual source is the strongest aspect of VDSS in which no stacking is necessary to build up the signal. Previous work used the large moveout of the wide-angle reflection, phase SsPmp, relative to the direct S-wave arrival, phase Ss, to minimize the trade-off between bulk P-wave speed (VP) and thickness of the crust (H). It is then straightforward to use the timing of the phase Sp to constrain VS. As examples, we show that this method works for data from both temporary and permanent seismic deployments in contrasting tectonic settings. Specifically, VS under station FORT in western Australia and H1620 in central Tibet are 3.77±0.08 and 3.42±0.11  km/s, respectively. This development complements the undertaking of using information from only the S-wave train to extract all three seismic parameters of the bulk crust, VP, VS, and H. These parameters are important for constraining overall silica content of the crust.

scholarly journals Predicting COVID-19 in very large countries: The case of Brazil

PLoS ONE ◽  
2021 ◽  
Vol 16 (7) ◽  
pp. e0253146
Author(s):  
V. C. Parro ◽  
M. L. M. Lafetá ◽  
F. Pait ◽  
F. B. Ipólito ◽  
T. N. Toporcov
Keyword(s):  
Health System ◽  
Linear Combination ◽  
Figure Of Merit ◽  
Model Fit ◽  
The Novel ◽  
System Utilization ◽  
Practical Proposal ◽  
Free Parameters ◽  
Using Data

This work presents a practical proposal for estimating health system utilization for COVID-19 cases. The novel methodology developed is based on the dynamic model known as Susceptible, Infected, Removed and Dead (SIRD). The model was modified to focus on the healthcare system dynamics, rather than modeling all cases of the disease. It was tuned using data available for each Brazilian state and updated with daily figures. A figure of merit that assesses the quality of the model fit to the data was defined and used to optimize the free parameters. The parameters of an epidemiological model for the whole of Brazil, comprising a linear combination of the models for each state, were estimated considering the data available for the 26 Brazilian states. The model was validated, and strong adherence was demonstrated in most cases.

scholarly journals Low uncertainty multifeature magnitude estimation with 3-D corrections and boosting tree regression: application to North Chile

2019 ◽  
Vol 220 (1) ◽  
pp. 142-159
Author(s):  
Jannes Münchmeyer ◽  
Dino Bindi ◽  
Christian Sippl ◽  
Ulf Leser ◽  
Frederik Tilmann
Keyword(s):  
Magnitude Estimation ◽  
Data Availability ◽  
P Wave ◽  
Machine Learning Techniques ◽  
Correction Function ◽  
Single Station ◽  
Correction Terms ◽  
Low Uncertainty ◽  
Non Parametric ◽  
Magnitude Estimates

SUMMARY Magnitude estimation is a central task in seismology needed for a wide spectrum of applications ranging from seismicity analysis to rapid assessment of earthquakes. However, magnitude estimates at individual stations show significant variability, mostly due to propagation effects, radiation pattern and ambient noise. To obtain reliable and precise magnitude estimates, measurements from multiple stations are therefore usually averaged. This strategy requires good data availability, which is not always given, for example for near real time applications or for small events. We developed a method to achieve precise magnitude estimations even in the presence of only few stations. We achieve this by reducing the variability between single station estimates through a combination of optimization and machine learning techniques on a large catalogue. We evaluate our method on the large scale IPOC catalogue with >100 000 events, covering seismicity in the northern Chile subduction zone between 2007 and 2014. Our aim is to create a method that provides low uncertainty magnitude estimates based on physically meaningful features. Therefore we combine physics based correction functions with boosting tree regression. In a first step, we extract 110 features from each waveform, including displacement, velocity, acceleration and cumulative energy features. We correct those features for source, station and path effects by imposing a linear relation between magnitude and the logarithm of the features. For the correction terms, we define a non-parametric correction function dependent on epicentral distance and event depth and a station specific, adaptive 3-D source and path correction function. In a final step, we use boosting tree regression to further reduce interstation variance by combining multiple features. Compared to a standard, non-parametric, 1-D correction function, our method reduces the standard deviation of single station estimates by up to $57\, {\rm per\, cent}$, of which $17\, {\rm per\, cent}$ can be attributed to the improved correction functions, while boosting tree regression gives a further reduction of $40\, {\rm per\, cent}$. We analyse the resulting magnitude estimates regarding their residuals and relation to each other. The definition of a physics-based correction function enables us to inspect the path corrections and compare them to structural features. By analysing feature importance, we show that envelope and P wave derived features are key parameters for reducing uncertainties. Nonetheless the variety of features is essential for the effectiveness of the boosting tree regression. To further elucidate the information extractable from a single station trace, we train another boosting tree on the uncorrected features. This regression yields magnitude estimates with uncertainties similar to the single features after correction, but without using the earthquake location as required for applying the correction terms. Finally, we use our results to provide high precision magnitudes and their uncertainties for the IPOC catalogue.

Empirical path corrections for regional-phase amplitudes

1999 ◽  
Vol 89 (2) ◽  
pp. 384-393 ◽  
Author(s):  
W. Scott Phillips
Keyword(s):  
Seismic Data ◽  
Variance Reduction ◽  
Seismic Energy ◽  
Central China ◽  
Wave Guide ◽  
The Tibetan Plateau ◽  
Order Of Magnitude ◽  
Using Data ◽  
Phase Amplitude ◽  
Test Ban

Abstract Using data from 385 events recorded at Lanzhou in central China, I compare two empirical methods for predicting and correcting for path effects on regional-phase amplitude ratios. The first method interpolates source- and distance-corrected seismic data to create geographical, path-correction surfaces. The second, or wave-guide, method employs correlations with path-averaged physical data such as topography to correct the seismic data. Path corrections can vary over an order of magnitude, and their use will sharpen differences in regional-phase ratios arising from different types of natural and man-made sources of seismic energy and, thus, will be important for monitoring a Comprehensive Test Ban Treaty. For Pg/Lg phase ratios in the band 0.5 to 1 Hz, interpolated path corrections reduced variance best using kriging (62%) and nearly as well using a radius 250 km, moving-window-mean smoother (56%). Wave-guide methods based on mean and rms topography reduced variance by 43%. Variance reduction is given relative to the standard correction for distance alone. Wave-guide methods were further tested by attempting to find correlations with topographic data that had been rotated geographically. For conservatively chosen sets of wave-guide parameters, the true orientations yielded the best variance reduction, adding confidence to the use of this method. Wave-guide methods complement interpolation methods because they extrapolate behavior beyond active seismic areas. However, I find broad regions that are fit poorly by wave-guide predictions, especially where the path effect changes rapidly, such as along the eastern edge of the Tibetan plateau where Pg/Lg ratios are underpredicted. The two methods can be combined using Bayesian kriging, forcing predictions to fit the data in seismically active areas and allowing more powerful extrapolation beyond.

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