Precise Relative Magnitude and Relative Location Estimates of Low-Yield Industrial Blasts in Pennsylvania

2020 ◽  
Vol 110 (1) ◽  
pp. 226-240
Author(s):  
Jonas A. Kintner ◽  
Charles J. Ammon ◽  
Kyle Homman ◽  
Andrew Nyblade
Keyword(s):  
Cross Correlation ◽  
Relative Magnitude ◽  
Time Shift ◽  
Relative Location ◽  
Mining Operations ◽  
Small Magnitude ◽  
Explosion Monitoring ◽  
Short Period ◽  
Local Shear ◽  
Seismic Networks

ABSTRACT Low-yield explosion monitoring requires the use of nearby short-period observations, which exhibit sensitivities to geologic heterogeneity and have low signal-to-noise ratios compared to larger events. In this study, we analyze 843 seismic events using nearly 475,000 individual observations to compute precise relative locations of small (1<ML<3) industrial explosions across Pennsylvania using local shear-wave and short-period, near-regional distance shear and surface-wave observations. We show that common-station, nearby event cross-correlation time-shift measurements reduce much of the complexity in wave propagation caused by regional geological heterogeneity. The resulting high-precision relative location estimates (with formal location uncertainties of tens of meters in some cases) allow us to image the time-dependent migration of the blast wall for several mines across Pennsylvania. In areas with two or more mines, the relative locations collapse a diffuse distribution of small-magnitude industrial events into discrete clusters associated with particular mining operations. We also use cross-correlation amplitudes to estimate more precise relative event magnitudes. We find that the relative magnitudes are generally consistent with the catalog magnitudes but improve the relationship between the reported amount of explosives used and event size for several mining operations throughout Pennsylvania. This work adds to existing demonstrations of how dense regional seismic networks are valuable for small-event monitoring and characterization, while also corroborating earlier works indicating the ability of cross-correlation methods to achieve precise relative location and magnituode estimates from local and regional observations of low-yield seismic sources.

Local-Distance Seismic Event Relocation and Relative Magnitude Estimation, Applications to Mining Related Seismicity in the Powder River Basin, Wyoming

2021 ◽  
Author(s):  
Jonas A. Kintner ◽  
K. Michael Cleveland ◽  
Charles J. Ammon ◽  
Andrew Nyblade
Keyword(s):  
Relative Magnitude ◽  
Powder River Basin ◽  
Seismic Sources ◽  
Seismic Events ◽  
Explosion Monitoring ◽  
Location Uncertainty ◽  
Short Period ◽  
Uncertainty Estimates ◽  
Local Distance ◽  
Industrial Mining

ABSTRACT Recent efforts to characterize small (Mw<3) seismic events at local distances have become more important because of the increased observation of human-triggered and induced seismicity and the need to advance nuclear explosion monitoring capabilities. The signals generated by low-magnitude seismic sources necessitate the use of nearby short-period observations, which are sensitive to local geological heterogeneity. Local to near-regional distance (<300  km) surface and shear waves can dominate short-period observations from small, shallow seismic sources. In this work, we utilize these observations to estimate precise, relative locations and magnitudes of ∼700 industrial mining events in Wyoming, using nearly 360,000 observations. The precise, relative location estimates (with formal location uncertainty estimates of less than 1 km) collapse a diffuse collection of mining events into discrete clusters associated with individual blasting operations. We also invert the cross-correlation amplitudes to estimate precise, relative moment magnitude estimates, which help validate and identify disparities in the event sizes reported by regional network catalogs. Joint use of multiple phases allows for the inclusion of more seismic events due to the increase in the number of observations. In some cases, using a single phase allowed us to relocate only 50% of the original reported seismic events within a cluster. Combining shear- and surface-wave phases increased the number of events to above 90% of the original events, allowing us to characterize a broader range of event sizes, source to station distances, and event distributions. This analysis takes a step toward making a fuller characterization of small industrial seismic events observed at local distances.

The foreshock sequence of the 1986 Chalfant, California, earthquake

1988 ◽  
Vol 78 (1) ◽  
pp. 172-187
Author(s):  
Kenneth D. Smith ◽  
Keith F. Priestley
Keyword(s):  
Main Shock ◽  
Slip Surface ◽  
Body Waves ◽  
Aftershock Distribution ◽  
Time Period ◽  
Main Shocks ◽  
Short Period ◽  
Local Shear ◽  
Stress Drops ◽  
Foreshock Activity

Abstract The ML 6.4 Chalfant, California, earthquake of 21 July 1986 was preceded by an extensive foreshock sequence. Foreshock activity is characterized by shallow clustering activity, including 7 events greater than ML 3, beginning 18 days before the earthquake, an ML 5.7 foreshock 24 hr before the main shock that ruptured only in the upper 10 km of the crust, and an “off-fault” cluster of activity perpendicular to the slip surface of the ML 5.7 foreshock associated with the hypocenter of the main shock. The Chalfant sequence occurred within the local short-period network, and the spatial and temporal development of the foreshock sequence can be observed in detail. Seismicity of the July 1986 time period is largely confined to two nearly conjugate planes; one striking N30°E and dipping 60° to the northwest associated with the ML 5.7 foreshock and the other striking N25°W and dipping 70° to the southwest associated with the main shock. Focal mechanisms for the foreshock period fall into two classes in agreement with these two planes. Shallow clustering of earthquakes in July and the ML 5.7 principal foreshock occur at the intersection of the two planes at a depth of approximately 7 km. The seismic moments determined from inversion of the teleseismic body waves are 4.2 × 1025 and 2.5 × 1025 dyne-cm for the principal foreshock and the main shock, respectively. Slip areas for these two events can be estimated from the aftershock distribution and result in stress drops of 63 bars for the principal foreshock and 16 bars for the main shock. The main shock occurred within an “off-fault” cluster of earthquakes associated with the principal foreshock. This cluster of activity occurs at a predicted local shear stress high in relation to the slip surface of the 20 July earthquake, and this appears to be the triggering mechanism of the main shock. The shallow rupture depth of the principal foreshock indicates that this event was anomalous with respect to the character of main shocks in the region.

Accuracy of determination of epicenter and origin time of small-magnitude earthquakes in the Indian subcontinent

1973 ◽  
Vol 63 (6-1) ◽  
pp. 1901-1912
Author(s):  
Harsh K. Gupta ◽  
Dragutin Skoko ◽  
Yasuo Satô
Keyword(s):  
Indian Subcontinent ◽  
Earth Model ◽  
Origin Time ◽  
Small Magnitude ◽  
Seismic Stations ◽  
The North ◽  
South Indian ◽  
The Monte Carlo Method ◽  
Time Determination ◽  
Seismic Networks

Abstract World seismicity maps prepared by plotting epicenters without considering their magnitude and the distribution of seismic stations may not represent true seismicity, since many earthquakes of small magnitude are not reported from regions having poor seismic networks. This situation is particularly noticeable in the Asian parts of the Alpide belt. Using the Monte Carlo method, errors of epicenter location and origin-time determination by the Indian network of seismic stations have been estimated for earthquakes in the Indian subcontinent. A simplified earth model has been used, and the calculations have been carried out for mb values of 5.0, 4.5, and 4.0. The results are compared with similar error estimations for the Romanian region where a better network of seismic stations enables location of all earthquakes of mb ≧ 4.2. This comparison shows that the errors for the central and the south Indian regions are comparable to those of Romania. However, the much larger errors in the north and northeastern regions show the necessity of establishing seismological observatories equipped with sensitive seismographs close to the foothills of the Himalayas.

Picking noisy refraction data using semblance supplemented by a Monte Carlo procedure and spectral balancing

1987 ◽  
Vol 77 (3) ◽  
pp. 942-957
Author(s):  
C. A. Zelt ◽  
J. J. Drew ◽  
M. J. Yedlin ◽  
R. M. Ellis
Keyword(s):  
Monte Carlo ◽  
Cross Correlation ◽  
Signal To Noise Ratio ◽  
Time Shift ◽  
Head Wave ◽  
Signal To Noise ◽  
Seismic Section ◽  
Monte Carlo Procedure ◽  
Noise Ratio ◽  
Refraction Data

Abstract In crustal refraction experiments, the crucial deeply refracted and head wave arrivals often have a low signal-to-noise ratio. A method to aid in the picking of noisy refraction data is presented which is applicable to any branch of a seismic section whose waveform is approximately invariant throughout the branch. The technique exploits the spatial correlation of arrivals and is based on the lateral coherency which results if the refracted arrivals are aligned by applying appropriate time shifts to each trace of the branch. The alignment of arrivals occurs iteratively and is accomplished through a cross-correlation of each trace with the stack of the section of the previous iteration. The iteration yielding the section with the highest degree of lateral coherency (semblance) is used to extract the travel-time pick of each trace. The pick, plus a possible d.c. component, is the negative of the time shift required to achieve arrival alignment. Two modifications can improve the performance of the picking routine. To prevent a cycle skipping problem, a Monte Carlo technique is implemented in which the cross-correlation function is transformed into a probability distribution so that the lag corresponding to the maximum cross-correlation is most probably selected. Second, to increase the coherency of the arrivals, a spectral balancing technique is applied in either the time or frequency domain. The picking routine is applied to both a synthetic and real data example, and the results suggest that the routine can be applied successfully to data with a signal-to-noise ratio as low as one. Also, the Monte Carlo procedure together with spectral balancing increases the final semblance over that obtained with the unmodified method.

Local Richter magnitude and total signal duration in southern California

1973 ◽  
Vol 63 (5) ◽  
pp. 1809-1827 ◽  
Author(s):  
Charles R. Real ◽  
Ta-Liang Teng
Keyword(s):  
Southern California ◽  
Epicentral Distance ◽  
Total Duration ◽  
Signal Duration ◽  
Local Magnitude ◽  
Total Signal ◽  
Source Effects ◽  
Short Period ◽  
Seismic Networks ◽  
Southern California Region

abstract Seismograms of 320 earthquakes (1,486 observations) from short-period seismometers occurring from January 1969 to April 1971 and 91 earthquakes (257 observations) during 1971 have been used to establish a relationship between total signal duration and the local Richter magnitude for the CIT and BHSN telemetered seismic networks in southern California. The data have been fitted using regression analysis to relationships of the form M τ = C 0 + C 1 log ⁡ τ + C 2 Δ M τ ≦ 3.8 M τ = C 0 + C 1 ( log ⁡ τ ) 2 + C 2 Δ M τ > 3.8 where τ is the total duration in seconds and Δ is the epicentral distance in kilometers. These relations explain up to 88 per cent (CIT) and 94 per cent (BHSN) of the variation in the data and yield magnitudes having standard deviations as low as 0.15 (CIT) and 0.14 (BHSN) magnitude units. It has been found that the local magnitude based on signal duration is relatively insensitive to variations in azimuth and source effects. In view of the limited distribution and low magnifiation of the Wood-Anderson torsion seismometer, and the previously recognized problems of “saturation” and instrument response associated with the amplitude technique, it is concluded that the method of duration applied to vertical short-period seismograph records will greatly improve the assignment of local magnitude to earthquakes in the southern California region.

scholarly journals Seismic scatterers in the lower mantle near subduction zones

2019 ◽  
Vol 219 (Supplement_1) ◽  
pp. S2-S20 ◽  
Author(s):  
Satoshi Kaneshima
Keyword(s):  
Oceanic Crust ◽  
Lower Mantle ◽  
Subduction Zones ◽  
P Waves ◽  
Waveform Data ◽  
Basaltic Rocks ◽  
Short Period ◽  
Subducted Oceanic Crust ◽  
Conversion Depth ◽  
Seismic Networks

SUMMARY We investigate the global distribution of S-to-P scatterers in the shallow to mid-lower mantle beneath subduction zones, where deep seismicity extends down to the bottom of the upper mantle. By array processing broadband and short period waveform data obtained at seismic networks, we seek anomalous later phases in the P coda within about 15–150 s after direct P waves. The later phases usually arrive along off-great circle paths and significantly later than S-to-P conversion from the ‘660 km’ discontinuity, often show positive slowness anomalies relative to direct P, and do not show a conversion depth that is consistent among nearby events. They are thus adequately regarded as scattered waves, rather than conversion at a global horizontal discontinuity. The S-to-P scattered waves often show amplitudes comparable to ‘S660P’ waves, which indicates that a spatial change in elastic properties by several percent occurs at the scatterers as abruptly as the post-spinel transformation and should arise from compositional heterogeneity. We locate prominent S-to-P scatterers beneath Pacific subduction zones and beneath southern Spain. Nearly half of 137 S-to-P scatterers located in this study and previous studies by the authors are shallower than 1000 km, and the number of scatterers decreases with depth. Scatterers deeper than 1800 km are rare and mostly weak. We examine relations between the locations of the scatterers and recently subducted slabs inferred from seismic tomography. The scatterers of mid-mantle depths, deeper than about 1000 km, are located distant from tomographic slabs. On the other hand, the majority of shallower scatterers are located beneath the slabs rather than near their fastest portions, which would indicate that chemically heterogeneous materials are not extensively entrained within thickened and folded slabs when the slabs impinge on the lower mantle. We also find scatterers near the locations where basaltic rocks of recently subducted oceanic crust are expected to exist, which suggests that oceanic crust is not delaminating when slabs impinge on the lower mantle.

Effect of the water layer on seismic noise cross-correlation across the Northeast Atlantic, from Madeira and Canaries to the Atlas-Gibraltar zone

2020 ◽  
Author(s):  
Graça Silveira ◽  
Joana Carvalho ◽  
Juan Pinzon ◽  
Susana Custódio ◽  
Carlos Corela ◽  
...  
Keyword(s):  
Group Velocity ◽  
Seismic Noise ◽  
Cross Correlation ◽  
Mode Conversion ◽  
Water Layer ◽  
Velocity Range ◽  
Crust And Upper Mantle ◽  
Northeast Atlantic ◽  
Short Period ◽  
Noise Cross Correlation

<p>One of the aims of project SIGHT (SeIsmic and Geochemical constraints on the Madeira HoTspot system) is to obtain a 3D model of SV-wave velocities of the crust and upper mantle of the Northeast Atlantic area encompassing Madeira and Canary Islands to the Atlas-Gibraltar zone, using seismic noise cross-correlations in the period range 2-100 s. Ambient noise cross-correlation has been successfully applied in a variety of tectonic environments to image the structure of the Earth subsurface. This technique overcomes some limitations ascribed to source–receiver geometry and sparse and irregular earthquake distribution, allowing to image Earth structure with a resolution that mainly depends on the network design. However, the effect of the water layer in the short period Empirical Green Functions, which are obtained by seismic noise cross-correlation, for interstation paths crossing the ocean is still poorly understood.</p><p>In several studies, it has been observed that the presence of water and sediments is responsible for later wave-train arrivals. Those later arrivals are frequently disregarded when measuring group velocity, either by considering only longer periods or by specifying a given velocity range.</p><p>In this work, we present a systematic study of the influence of the water layer on both vertical and radial synthetic Rayleigh waves, as well as on higher-mode conversion and on the group velocities dispersion measurements.</p><p>We show that although the fundamental mode dominates, the presence of the first overtones at short periods (typically below 8 seconds) cannot be neglected. We also show that specifying a given velocity range when retrieving group velocity can result in a mixture of modes. Our tests reveal that, at short periods, the water has a dominant effect on ocean-continent laterally varying media.</p><p>This is a contribution to projects SIGHT (Ref. PTDC/CTA-GEF/30264/2017) and STORM (Ref. UTAP-EXPL/EAC/0056/2017). The authors would like to acknowledge the financial support FCT through project UIDB/50019/2020 – IDL.</p>

Seismotectonic setting of Santorini-Amorgos zone and the surrounding area revealed from crustal earthquakes relocation and Vp/Vs distribution

2020 ◽  
Author(s):  
Ratri Andinisari ◽  
Konstantinos I. Konstantinou ◽  
Pratul Ranjan ◽  
Qori F. Hermawan
Keyword(s):  
Cross Correlation ◽  
Double Difference ◽  
Surrounding Area ◽  
Submarine Volcano ◽  
S Wave ◽  
Offshore Area ◽  
Crustal Earthquakes ◽  
Wave Travel ◽  
Seismic Networks ◽  
Earthquake Clusters

<p>The Santorini-Amorgos zone represents right-lateral transtensional regime from NE of Santorini to the south of Amorgos which also hosts Kolumbo submarine volcano. A total number of 1869 crustal events from 2002 to 2019 were recorded by permanent and temporal seismic networks deployed in southern Aegean. Absolute locations of these events were obtained by utilizing the probabilistic nonlinear algorithm NonLinLoc. Precise relative relocation by using double-difference algorithm with catalog and cross-correlation differential times was later performed, resulting in 1455 locations with horizontal and vertical uncertainties of less than 0.3 km. Clusters of earthquakes relocated between Naxos and Paros as well as north of Astypalaia do not coincide with any fault in the area. Similarly, the relocated crustal events across Santorini-Amorgos zone show that most of the earthquake clusters do not coincide with any of the existing faults. The distribution of Vp/Vs ratios in the area were investigated based on the P and S-wave travel times of all the events. Vp/Vs ratios in the area vary between 1.67 and 2.03 with errors less than 0.04. The highest Vp/Vs values were found to be distributed in the area between Naxos and Paros. Other areas with notably high Vp/Vs ratio are north of Santorini, Anydros, west of Amorgos, offshore area south of the easternmost tip of Amorgos, and the island of Astypalaia. These mentioned areas were also rich in seismic activities during the period of study. The high Vp/Vs ratios in the region of high seismicity signifies that these events were likely related to the migration of magmatic fluids to the surface and may not be caused by the existing faults.</p>

scholarly journals Further measurements on wireless waves received from the upper atmosphere

1927 ◽  
Vol 116 (775) ◽  
pp. 682-693 ◽  
Keyword(s):  
Closed Loop ◽  
Wave Length ◽  
Direct Proof ◽  
Relative Magnitude ◽  
Upper Atmosphere ◽  
Circle Plane ◽  
The Earth ◽  
Direction Finder ◽  
Short Period ◽  
Attention To Detail

In previous papers the authors have described the development of experimental methods of measuring the directions and relative intensities of both the electric and magnetic forces in wireless waves received at the earth’s surface from a distant transmitting station. In this work it was seen that the detection of the arrival of waves deflected from the upper atmosphere, and polarised with their electric force in a horizontal plane, was rendered difficult owing to the relatively great reflecting powTer of the earth resulting from its high conductivity. By a suitable choice of wave-length and careful attention to detail in the design and construction of the apparatus, however, the methods employed enabled measurements to be made on both vertically and horizontally polarised waves. The results of such measurements enabled a direct proof to be given of the fact that the fading of wireless signals on a vertical aerial and the variations of bearings experienced on the closed-loop type of wireless direction-finder are due to the reception respectively of vertically and horizontally polarised waves deflected from the upper atmosphere in their passage from the transmitter to the receiver. On arrival at the receiver, these indirect or atmospheric waves interfere with the direct or ground waves, in a manner determined by their relative magnitude and phase, and produce the intensity and apparent direc­tional variations mentioned above. The results of such interference phenomena have been investigated experimentally by Appleton and Barnett and by Holling-worth. In a more recent publication the present authors have provided experimental evidence showing that the path of the indirect waves is confined to the great circle plane between the transmitter and receiver. The measurements of the quantities in the received waves as previously described by the authors were confined to observations on the transmissions from the Bournemouth broadcasting station over a short period. The object of the present paper is to describe the continuation of these measurements and their extension to the transmissions from other stations.

scholarly journals Automated Threshold Determination of Auditory Evoked Brainstem Responses by Cross-correlation Analysis with Varying Sweep Number

2019 ◽  
Author(s):  
Haoyu Wang ◽  
Bei Li ◽  
Xu Ding ◽  
Xueling Wang ◽  
Zhiwu Huang ◽  
...  
Keyword(s):  
Cross Correlation ◽  
Test Procedure ◽  
Auditory Brainstem ◽  
Time Shift ◽  
Strong Response ◽  
Reliable Determination ◽  
Threshold Determination ◽  
Cross Correlation Analysis ◽  
Brainstem Response

ABSTRACTAuditory brainstem response (ABR) is widely employed to evaluate the hearing function, both in clinics and basic research. Despite many attempts for automation over decades, reliable determination of threshold stimulus level still relies on human visual identification of waveform, which oftentimes is subjective. Here, we report a robust procedure for automatic and accurate threshold determination in both mouse and human ABR. Contrary to prior approaches, in our new threshold determination algorithm, the on-going averaging is stopped once the waveform is confirmed by a cross-correlation time shift approach. The flexible ending sweep numbers for different stimuli is used to inform the threshold determination. We found a good match of the threshold readings between the algorithm and the human judges. Moreover, in the algorithm, smaller sweep number is required for strong response from supra-threshold level, and thus a considerable portion of sweeps can be saved in comparison to the case with level averaging of a fix number. These features are attractive and implementation of this method in commercial devices will make the ABR test procedure more objective and efficient.

Sign in / Sign up

Export Citation Format

Share Document