Source spectral characteristics of Miramichi earthquakes: Results from 115 P-wave observations

1989 ◽  
Vol 79 (1) ◽  
pp. 15-30
Author(s):  
Kin-Yip Chun ◽  
Richard J. Kokoski ◽  
Gordon F. West
Keyword(s):  
High Frequency ◽  
Dynamic Range ◽  
Spectral Characteristics ◽  
Sampling Rate ◽  
Spectral Ratio ◽  
P Wave ◽  
P Waves ◽  
Single Station ◽  
Source Scaling ◽  
Source Models

Abstract Source scaling relation is studied over the magnitude (mN) range 2.6 to 5.4 using P waves generated by 31 tightly clustered earthquakes in New Brunswick, Canada. The recording stations, six in total, have a 60-points/sec sampling rate and a dynamic range of about 100 dB. They are located at regional distance (188 to 448 km), with a wide azimuthal coverage. The data interpreted consist of 115 spectral ratio curves (2-20 Hz), each obtained in a manner that allows effective cancellation of the effects caused by source radiation pattern, path attenuation, geometrical spreading, instrument error, and variability in site function. The data selected in this study differ from the single-station records used in a previous source-scaling study of Miramichi earthquakes (Chael, 1987) in having: 1) broader distance coverage; 2) greater recording dynamic range; 3) higher Nyquist frequency; and 4) larger data size. We conclude from the observed spectral ratios that source models having an ω−2 high-frequency fall-off (ω-square model) are strongly favored by the data over those having an ω−3 high-frequency fall-off (ω-cube model) and that stress drop increases with moment at a rate proposed earlier by Nuttli (1983a, b).

Propagation of high-frequency (4- to 50-Hz) P waves in the northeastern United States

1995 ◽  
Vol 85 (4) ◽  
pp. 1244-1248
Author(s):  
Eric P. Chael ◽  
Patrick J. Leahy ◽  
Jerry A. Carter ◽  
Noël Barstow ◽  
Paul W. Pomeroy
Keyword(s):  
United States ◽  
Decay Rate ◽  
High Frequency ◽  
P Wave ◽  
Wave Spectra ◽  
Northeastern United States ◽  
P Waves ◽  
Geometric Spreading ◽  
Frequency Independent

Abstract We have measured the decay rate of high-frequency (4- to 50-Hz) P waves in the northeastern United States. We analyzed signals from 28 explosions of a 1988 USGS/AFGL/GSC refraction survey recorded at distances between 30 and 400 km. Over this range, the decay rate steadily increases from Δ−2 at 10 Hz to Δ−4 at 45 Hz. If one assumes geometric spreading of Δ−1.3, then the remaining decay is consistent with a nearly frequency-independent Q of about 1000. The results provide a useful parameterization for predicting P-wave spectra at near-regional ranges.

scholarly journals Synchronous Mixing Architecture for Digital Bandwidth Interleaving Sampling System

Electronics ◽  
2021 ◽  
Vol 10 (16) ◽  
pp. 1998
Author(s):  
Xiaochang Jiang ◽  
Jie Wu ◽  
Yubo Ma
Keyword(s):  
High Frequency ◽  
Dynamic Range ◽  
Sampling Rate ◽  
Poor Performance ◽  
Sampling System ◽  
Analog To Digital ◽  
Frequency Components ◽  
Time Interleaved ◽  
Evaluation Platform ◽  
Hybrid Filter Bank

By using a mixer to down-convert the high frequency components of a signal, digital bandwidth interleaving (DBI) technology can simultaneously increase the sampling rate and bandwidth of the sampling system, compared to the time-interleaved and hybrid filter bank. However, the software and hardware of the classical architecture are too complicated, which also leads to poor performance. In particular, the pilot tone used to synchronize the analog and digital local oscillators (LO) of mixers intermodulates with the high frequency components of the signal, resulting in larger spurs. This paper proposes a synchronous mixing architecture for the DBI system, where the LO of the analog mixer is synchronized with the sampling clock of the analog-to-digital converter. Its hardware and software are simplified—the pilot tone used to synchronize the LOs can also be removed. An evaluation platform with a sampling rate of 250 MSPS is implemented to illustrate the performance of the new architecture. The result shows that the spurious free dynamic range (SFDR) of the new architecture is more than 20 dB higher than the classical one in a high frequency range. The rise time of a step signal of the new architecture is 0.578 ± 0.070 ns faster than the classical one with the same bandwidth (90 MHz).

Relation between P- and S-wave corner frequencies in the seismic spectrum

1974 ◽  
Vol 64 (6) ◽  
pp. 1621-1627 ◽  
Author(s):  
J. C. Savage
Keyword(s):  
High Frequency ◽  
Body Wave ◽  
Fault Model ◽  
P Wave ◽  
Corner Frequency ◽  
Rupture Propagation ◽  
S Wave ◽  
P Waves ◽  
Fault Surface ◽  
S Waves

abstract A comprehensive set of body-wave spectra has been calculated for the Haskell fault model generalized to a circular fault surface. These spectra are used to show that in practice the P-wave corner frequency (ƒp) may exceed the S-wave corner frequency (ƒs) when near-sonic or transonic rupture propagation obtains. The explanation appears to be that in such cases ƒs is so large that it is not identified within the recorded band, but rather a secondary corner is mistaken for ƒs. As a consequence of failing to detect the true asymptotic trend, the high-frequency falloff of the spectrum with frequency is substantially less for S waves than for P waves. This explanation appears to be consistent with the demonstration by Molnar, Tucker, and Brune (1973) that ƒp may exceed ƒs.

Near-source effects on regional seismograms: An analysis of the NTS explosions PERA and QUESO

1991 ◽  
Vol 81 (6) ◽  
pp. 2371-2394
Author(s):  
Steven R. Taylor ◽  
John T. Rambo ◽  
Robert P. Swift
Keyword(s):  
Shock Wave ◽  
High Frequency ◽  
Spectral Characteristics ◽  
Low Frequency ◽  
Spectral Ratio ◽  
Corner Frequency ◽  
Burial Depth ◽  
Wave System ◽  
Spectral Ratios ◽  
Remarkable Similarity

Abstract A comparative analysis of two closely spaced Nevada Test Site explosions, PERA and QUESO, is made to study the effects of near-source phenomena on regional-wave excitation. Although the two explosions were of similar size, burial depth, and only separated by 4 km, the 1 to 2 and 6 to 8 Hz regional-wave spectral ratio for QUESO is anomalously low (a factor of 10 smaller than that of PERA). Examination of the regional and close-in spectra for each event shows a remarkable similarity and suggests that QUESO has less low-frequency and more high-frequency energy than PERA. These observations may be caused by a 564 m3, funnel-shaped region filled with unconsolidated sand and a possible void directly above the QUESO detonation point. Close-in observations suggest that this region may have partially decoupled the up-going energy from QUESO, resulting in a reduction of the low-frequency energy. The high-frequency enhancement for QUESO may be due to the rapid loss of energy to nonlinear effects such as greater pore collapse and fracturing in the anomalous region. This resulted in the radiation of more impulsive, shorter-duration waveforms producing a higher corner frequency and less-rapid high-frequency spectral decay for QUESO. For PERA, the loss of energy to a two-wave system occurred more slowly and over a larger volume, resulting in a broader source pulse typical of explosions in porous materials. Comparison of shock radius versus time data suggests that the shock wave was strongly affected in the anomalous zone a few meters above the QUESO device. One-dimensional finite-difference calculations with and without a partial decoupling region within 8 m of the device are consistent with the observations. Although spallation was reduced for QUESO, simulations using a finite spall model indicate that the spall spectral peak should be centered at about 3 to 7 Hz and probably did not significantly contribute to the reduced spectral ratio. The remarkable similarity of the PERA/QUESO spectral ratios taken at distances of 90 m and 400 km suggests that the spectral characteristics of explosions are established in close proximity to the source. Although depth-dependent effects of attenuation acting at small strains may enhance the differences in spectral ratios between NTS explosions and western U.S. earthquakes, these effects are probably secondary to the high-pressure, high strain-rate dynamic material response to the radiated explosion shock wave. These observations point out the importance of up-going energy on the generation of regional phases from explosions. Because of reduced overburden pressures above the detonation point, large nonlinear deformations predominate in this region and appear to affect all of the signals except perhaps the very initial part of the Pn waveform.

Spectral discrimination between NTS explosions and Western United States earthquakes at regional distances

1988 ◽  
Vol 78 (4) ◽  
pp. 1563-1579
Author(s):  
Steven R. Taylor ◽  
Nevin W. Sherman ◽  
Marvin D. Denny
Keyword(s):  
United States ◽  
High Frequency ◽  
Source Region ◽  
Spectral Ratio ◽  
Source Model ◽  
Pressure Effects ◽  
Western United States ◽  
Dislocation Source ◽  
Overburden Pressure ◽  
Single Station

Abstract Spectral ratio disciminants are applied to 72 Western United States earthquakes and 64 NTS explosions recorded at four broadband seismic stations surrounding NTS. The ratio of the energy in the 1- to 2- and 6- to 8-Hz bands for Pn, Pg, and Lg is calculated and a simple distance correction applied to the data. The spectral ratio appears to have potential as a disciminant at relatively small magnitudes (3.0 < mb < 4.5) and single station misclassification probabilities for detected phases range from 4 to 33 per cent, with Lg showing the best performance followed by Pg and Pn. Below mb 4.5 to 5.0, the earthquakes are observed to have more high-frequency energy than the explosions for all three phases. This observation may be due to actual source differences or to depth-dependent effects of attenuation on the shallow explosions and deeper earthquakes. At higher magnitudes, the two populations merge and discrimination is poor. Overburied explosions are characterized by the existence of more high-frequency energy than those at standard containment depths and are often misclassified. The Brune dislocation source model is shown to satisfactorily fit the earthquake spectral ratios plotted as a function of mb for reasonable stress drops. However, the Mueller-Murphy explosion source model has problems predicting the decrease in the explosion spectral ratio observed at higher magnitudes (mb > 4.5 to 5.0). This may be due to uncertainties in the apparent source-time function for explosions. These complications may be due to changes in the dynamic response of the material in the near-source region as a function of overburden pressure, effects of secondary sources, or to variations in regional phase excitation with depth.

scholarly journals Antarctic ice-sheet structures retrieved from P-wave coda autocorrelation method and comparisons with two other single-station passive seismic methods

2019 ◽  
Vol 66 (255) ◽  
pp. 153-165
Author(s):  
Peng Yan ◽  
Zhiwei Li ◽  
Fei Li ◽  
Yuande Yang ◽  
Weifeng Hao
Keyword(s):  
Ice Sheet ◽  
Spectral Ratio ◽  
Receiver Functions ◽  
P Wave ◽  
Polar Regions ◽  
Seismic Methods ◽  
Single Station ◽  
Passive Seismic ◽  
Glacier Ice ◽  
Autocorrelation Method

AbstractPassive seismology is becoming increasingly popular for glacier/ice-sheet structure investigations in Polar regions. Single-station passive seismic methods including P-wave receiver functions (PRFs), horizontal-to-vertical spectral ratio (HVSR) and a recently proposed autocorrelation method have been used to retrieve glacier/ice-sheet structures. Despite their successful applications, analysis regarding their detection abilities in different glaciological environments has not been reported. In this study, we compare ice thicknesses and vp/vs ratios obtained from the three methods using data collected at GAMSEIS and POLENET/ANET seismic arrays in Antarctica. Ice thickness estimates derived from the three methods are found to be consistent. Comparisons conducted under various model setups, including those involving tiled layers and sedimentary layers, show that the effectiveness of the autocorrelation method is not superior to the PRF method for retrieving ice-sheet structures. The autocorrelation method however can complement other methods as it only requires a single component seismic record.

Crustal structure of the Baltic Shield beneath Umeå, Sweden, from the spectral behavior of long-period P waves

1975 ◽  
Vol 65 (1) ◽  
pp. 113-126
Author(s):  
Lap Sau Leong
Keyword(s):  
Quantitative Measure ◽  
Spectral Ratio ◽  
Radial Component ◽  
P Wave ◽  
P Waves ◽  
Long Period ◽  
Recording Station ◽  
The Baltic ◽  
Lateral Variations ◽  
Teleseismic Events

abstract The method of spectral ratio response for crustal thickness determination beneath a receiving station, using long-period P waves of teleseismic events, has been applied. The purpose of this study is to investigate further the already well-depicted shield structure in Sweden beneath the WWSSN station at Umeå, the methodical procedure involved in this inversion problem, and possible sensitivity of the method to lateral variations of the shield area beneath the recording station. Teleseismic events from the Okhotsk Sea, Mongolia, and Hindu Kush regions are considered. Results suggest a value of 42 km for the two-layer crustal model beneath Umeå with possible lateral variations in velocity and/or dipping M-discontinuity surface to the east. It is proposed that a quantitative measure of the reliability of amplitudes and periodicity of peaks of the response ratios and indications of possible lateral anisotropy are obtained by treating the horizontal P-wave component both as a radial component of a three-component vector field and as being along the great circle through the epicenter and the receiving station.

scholarly journals Deep Neural Networks for Earthquake Detection and Source Region Estimation in North-Central Venezuela

2020 ◽  
Author(s):  
Ruben Tous ◽  
Leonardo Alvarado ◽  
Beatriz Otero ◽  
Leonel Cruz ◽  
Otilio Rojas
Keyword(s):  
Source Region ◽  
P Wave ◽  
Estimation Accuracy ◽  
Detection Accuracy ◽  
P Waves ◽  
North Central ◽  
Detection Algorithms ◽  
Earthquake Detection ◽  
Single Station ◽  
Seismic Records

ABSTRACT Reliable earthquake detection algorithms are necessary to properly analyze and catalog the continuously growing seismic records. We report the results of applying a deep convolutional neural network, called UPC-UCV (Universitat Politecnica de Catalunya - Universidad Central de Venezuela), over single-station three-channel signal windows for P-wave earthquake detection and source region estimation in north-central Venezuela. The analysis is performed on a new dataset of handpicked arrivals of P waves from local events, named CARABOBO, built and made public for reproducibility and benchmarking purposes. The CARABOBO dataset consists of three-channel continuous data recorded by the broadband stations of the Venezuelan Foundation for Seismological Research in the region of 9.5°–11.5°N and 67.0°–69.0°W during the time period from April 2018 to April 2019. During this period, 949 earthquakes were recorded in that area, corresponding to earthquakes with magnitudes in the range from Mw 1.1 to 5.2. To estimate the epicentral source region of a detected event, the proposed network employs geographical distribution of the CARABOBO dataset into K clusters as a basis. This geographical partitioning is automatically performed by the k-means algorithm, and the optimality of the K-values for our dataset has been assessed using the elbow (K=5) and silhouette (K=3) methods. For target seismicity, the proposed network achieves 95.27% detection accuracy and 93.36% source region estimation accuracy, when using K=5 geographic clusters. The location accuracy slightly increases to 95.68% in the case of K=3 geographic partitions. The detection capability of this network has also been tested on the OKLAHOMA dataset, which compiles more than 2000 local earthquakes that occurred in this U.S. state. Without any modification, the proposed network yields excellent detection results when trained and evaluated on that dataset (98.21% accuracy; ConvNetQuake, fine-tuned for this dataset, achieves a 97.32% accuracy), corresponding to a totally different geographical region.

scholarly journals FRCaMP, a Red Fluorescent Genetically Encoded Calcium Indicator Based on Calmodulin from Schizosaccharomyces Pombe Fungus

2020 ◽  
Vol 22 (1) ◽  
pp. 111
Author(s):  
Oksana M. Subach ◽  
Natalia V. Barykina ◽  
Elizaveta S. Chefanova ◽  
Anna V. Vlaskina ◽  
Vladimir P. Sotskov ◽  
...  
Keyword(s):  
Schizosaccharomyces Pombe ◽  
Hela Cells ◽  
Calcium Binding ◽  
Dynamic Range ◽  
Spectral Characteristics ◽  
Binding Domain ◽  
Calcium Transients ◽  
Neuronal Cultures ◽  
Decay Kinetics ◽  
Calcium Binding Domain

Red fluorescent genetically encoded calcium indicators (GECIs) have expanded the available pallet of colors used for the visualization of neuronal calcium activity in vivo. However, their calcium-binding domain is restricted by calmodulin from metazoans. In this study, we developed red GECI, called FRCaMP, using calmodulin (CaM) from Schizosaccharomyces pombe fungus as a calcium binding domain. Compared to the R-GECO1 indicator in vitro, the purified protein FRCaMP had similar spectral characteristics, brightness, and pH stability but a 1.3-fold lower ΔF/F calcium response and 2.6-fold tighter calcium affinity with Kd of 441 nM and 2.4–6.6-fold lower photostability. In the cytosol of cultured HeLa cells, FRCaMP visualized calcium transients with a ΔF/F dynamic range of 5.6, which was similar to that of R-GECO1. FRCaMP robustly visualized the spontaneous activity of neuronal cultures and had a similar ΔF/F dynamic range of 1.7 but 2.1-fold faster decay kinetics vs. NCaMP7. On electrically stimulated cultured neurons, FRCaMP demonstrated 1.8-fold faster decay kinetics and 1.7-fold lower ΔF/F values per one action potential of 0.23 compared to the NCaMP7 indicator. The fungus-originating CaM of the FRCaMP indicator version with a deleted M13-like peptide did not interact with the cytosolic environment of the HeLa cells in contrast to the metazoa-originating CaM of the similarly truncated version of the GCaMP6s indicator with a deleted M13-like peptide. Finally, we generated a split version of the FRCaMP indicator, which allowed the simultaneous detection of calcium transients and the heterodimerization of bJun/bFos interacting proteins in the nuclei of HeLa cells with a ΔF/F dynamic range of 9.4 and a contrast of 2.3–3.5, respectively.

scholarly journals High-frequency rectifiers based on type-II Dirac fermions

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Libo Zhang ◽  
Zhiqingzi Chen ◽  
Kaixuan Zhang ◽  
Lin Wang ◽  
Huang Xu ◽  
...  
Keyword(s):  
High Frequency ◽  
Dynamic Range ◽  
High Sensitivity ◽  
High Dynamic Range ◽  
Anisotropy Ratio ◽  
Dirac Fermions ◽  
Topological States ◽  
Topological Semimetals ◽  
Polarized Surface ◽  
Symmetry Protected

AbstractThe advent of topological semimetals enables the exploitation of symmetry-protected topological phenomena and quantized transport. Here, we present homogeneous rectifiers, converting high-frequency electromagnetic energy into direct current, based on low-energy Dirac fermions of topological semimetal-NiTe2, with state-of-the-art efficiency already in the first implementation. Explicitly, these devices display room-temperature photosensitivity as high as 251 mA W−1 at 0.3 THz in an unbiased mode, with a photocurrent anisotropy ratio of 22, originating from the interplay between the spin-polarized surface and bulk states. Device performances in terms of broadband operation, high dynamic range, as well as their high sensitivity, validate the immense potential and unique advantages associated to the control of nonequilibrium gapless topological states via built-in electric field, electromagnetic polarization and symmetry breaking in topological semimetals. These findings pave the way for the exploitation of topological phase of matter for high-frequency operations in polarization-sensitive sensing, communications and imaging.

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