Waveform Cross-Correlation-Based Differential Travel-Time Measurements at the Northern California Seismic Network

2005 ◽  
Vol 95 (6) ◽  
pp. 2446-2461 ◽  
Author(s):  
D. P. Schaff
Keyword(s):  
Travel Time ◽  
Cross Correlation ◽  
Seismic Network ◽  
Northern California ◽  
Waveform Cross Correlation

scholarly journals Teleseismic P waves at the AlpArray seismic network: wave fronts, absolute travel times and travel-time residuals

Solid Earth ◽  
2021 ◽  
Vol 12 (7) ◽  
pp. 1635-1660
Author(s):  
Marcel Paffrath ◽  
Wolfgang Friederich ◽  
Keyword(s):  
Travel Time ◽  
Cross Correlation ◽  
Field Experiments ◽  
Epicentral Distance ◽  
Seismic Network ◽  
Corner Frequency ◽  
Travel Times ◽  
Wave Fronts ◽  
P Waves ◽  
Waveform Cross Correlation

Abstract. We present an extensive dataset of highly accurate absolute travel times and travel-time residuals of teleseismic P waves recorded by the AlpArray Seismic Network and complementary field experiments in the years from 2015 to 2019. The dataset is intended to serve as the basis for teleseismic travel-time tomography of the upper mantle below the greater Alpine region. In addition, the data may be used as constraints in full-waveform inversion of AlpArray recordings. The dataset comprises about 170 000 onsets derived from records filtered to an upper-corner frequency of 0.5 Hz and 214 000 onsets from records filtered to an upper-corner frequency of 0.1 Hz. The high accuracy of absolute and residual travel times was obtained by applying a specially designed combination of automatic picking, waveform cross-correlation and beamforming. Taking travel-time data for individual events, we are able to visualise in detail the wave fronts of teleseismic P waves as they propagate across AlpArray. Variations of distances between isochrons indicate structural perturbations in the mantle below. Travel-time residuals for individual events exhibit spatially coherent patterns that prove to be stable if events of similar epicentral distance and azimuth are considered. When residuals for all available events are stacked, conspicuous areas of negative residuals emerge that indicate the lateral location of subducting slabs beneath the Apennines and the western, central and eastern Alps. Stacking residuals for events from 90∘ wide azimuthal sectors results in lateral distributions of negative and positive residuals that are generally consistent but differ in detail due to the differing direction of illumination of mantle structures by the incident P waves. Uncertainties of travel-time residuals are estimated from the peak width of the cross-correlation function and its maximum value. The median uncertainty is 0.15 s at 0.5 Hz and 0.18 s at 0.1 Hz, which is more than 10 times lower than the typical travel-time residuals of up to ±2 s. Uncertainties display a regional dependence caused by quality differences between temporary and permanent stations as well as site-specific noise conditions.

scholarly journals Teleseismic P-waves at the AlpArray seismic network: Wave fronts, absolute traveltimes and traveltime residuals

2020 ◽  
Author(s):  
Marcel Heinz Paffrath ◽  
Wolfgang Friederich ◽  
Keyword(s):  
Cross Correlation ◽  
Field Experiments ◽  
Epicentral Distance ◽  
Waveform Inversion ◽  
Eastern Alps ◽  
Seismic Network ◽  
P Waves ◽  
Full Waveform ◽  
Waveform Cross Correlation ◽  
Automatic Picking

Abstract. We present an extensive dataset of highly accurate absolute traveltimes and traveltime residuals of teleseismic P- waves recorded by the AlpArray Seismic Network and complementary field experiments in the years from 2015 to 2019. The dataset is intended to serve as the basis for teleseismic delay time tomography of the upper mantle below the greater Alpine region. In addition, the data may be used as constraints in full-waveform inversion of AlpArray recordings. The dataset comprises about 170.000 onsets derived from records filtered to 0.5 Hz and 214.000 onsets from records filtered to 0.1 Hz. The high accuracy of absolute and residual traveltimes was obtained by applying a specially designed combination of automatic picking, waveform cross-correlation and beam-forming. Taking traveltime data for individual events, we are able to visualize in detail the wavefronts of teleseismic P-waves as they propagate across AlpArray. Variations of distances between isochrons indicate structural perturbations in the mantle below. Traveltime residuals for individual events exhibit spatially coherent patterns that prove to be reproducible if events of similar epicentral distance and azimuth are considered. When residuals for all available events are stacked, conspicuous areas of negative residuals emerge that already indicate the lateral location of subducting slabs beneath the Apennines and the western, central and eastern Alps. Stacking residuals for events from 90 degree wide azimuthal sectors results in lateral distributions of negative and positive residuals that are generally consistent but differ in detail due to the differing direction of illumination of mantle structures by the incident P-waves. Comparing traveltimes from the 0.5 Hz and the 0.1 Hz dataset, we observe on average earlier arrivals in the 0.5 Hz dataset presumably caused by velocity dispersion. Uncertainties of traveltime residuals are estimated from the peak width of the cross-correlation function and its maximum value. The median uncertainty is 0.15 s at 0.5 Hz and 0.18 s at 0.1 Hz, way below the typical traveltime residuals of up to ±2 s. Uncertainties display a regional dependence caused by quality differences between temporary and permanent stations as well as location dependent noise conditions.

The first 20 years of CALNET, the Northern California seismic network

1992 ◽  
Author(s):  
D.H. Oppenheimer ◽  
Fred W. Klein ◽  
Jerry P. Eaton
Keyword(s):  
Seismic Network ◽  
Northern California

scholarly journals Do millennials value travel time differently because of productive multitasking? A revealed-preference study of Northern California commuters

2021 ◽  
Author(s):  
Aliaksandr Malokin ◽  
Giovanni Circella ◽  
Patricia L. Mokhtarian
Keyword(s):  
Older Adults ◽  
Young Adults ◽  
Willingness To Pay ◽  
Travel Time ◽  
Choice Model ◽  
Mode Choice ◽  
Revealed Preference ◽  
Northern California ◽  
Factors Affecting ◽  
The Impact

AbstractMillennials, the demographic cohort born in the last two decades of the twentieth century, are reported to adopt information and communication technologies (ICTs) in their everyday lives, including travel, to a greater extent than older generations. As ICT-driven travel-based multitasking influences travelers’ experience and satisfaction in various ways, millennials are expected to be affected at a greater scale. Still, to our knowledge, no previous studies have specifically focused on the impact of travel multitasking on travel behavior and the value of travel time (VOTT) of young adults. To address this gap, we use an original dataset collected among Northern California commuters (N = 2216) to analyze the magnitude and significance of individual and household-level factors affecting commute mode choice. We estimate a revealed-preference mode choice model and investigate the differences between millennials and older adults in the sample. Additionally, we conduct a sensitivity analysis to explore how incorporation of explanatory factors such as attitudes and propensity to multitask while traveling in mode choice models affects coefficient estimates, VOTT, and willingness to pay to use a laptop on the commute. Compared to non-millennials, the mode choice of millennials is found to be less affected by socio-economic characteristics and more strongly influenced by the activities performed while traveling. Young adults are found to have lower VOTT than older adults for both in-vehicle (15.0% less) and out-of-vehicle travel time (15.7% less), and higher willingness to pay (in time or money) to use a laptop, even after controlling for demographic traits, personal attitudes, and the propensity to multitask. This study contributes to better understanding the commuting behavior of millennials, and the factors affecting it, a topic of interest to transportation researchers, planners, and practitioners.

Use of Waveform Cross Correlation to Reconstruct the Aftershock Sequence of the August 14, 2016, Sakhalin Earthquake

2019 ◽  
Vol 55 (5) ◽  
pp. 544-558
Author(s):  
I. O. Kitov ◽  
S. B. Turuntaev ◽  
A. V. Konovalov ◽  
A. A. Stepnov ◽  
V. V. Pupatenko
Keyword(s):  
Cross Correlation ◽  
Aftershock Sequence ◽  
Waveform Cross Correlation

scholarly journals Distributed and Communication-Efficient Spatial Auto-Correlation Subsurface Imaging in Sensor Networks

Sensors ◽  
2019 ◽  
Vol 19 (11) ◽  
pp. 2427 ◽  
Author(s):  
Maria Valero ◽  
Fangyu Li ◽  
Jose Clemente ◽  
Wenzhan Song
Keyword(s):  
Sensor Networks ◽  
Ambient Noise ◽  
Cross Correlation ◽  
Seismic Velocity ◽  
Computational Cost ◽  
Seismic Network ◽  
Communication Process ◽  
Velocity Variation ◽  
Auto Correlation ◽  
Subsurface Monitoring

A wireless seismic network can be effectively used as a tool for subsurface monitoring and imaging. By recording and analyzing ambient noise, a seismic network can image underground infrastructures and provide velocity variation information of the subsurface that can help to detect anomalies. By studying the variation in the noise cross-correlation function of the noise, it is possible to determine the subsurface seismic velocity and image underground infrastructures. Ambient noise imaging can be done in a decentralized fashion using Distributed Spatial Auto-Correlation (dSPAC). In dSPAC over sensor networks, the cross-correlation is the most intensive communication process since nodes need to communicate their data with neighbor nodes. In this paper, a new communication-reduced method for cross-correlation is presented to meet bandwidth and cost of communication constraints in networks while ambient noise imaging is performed using dSPAC method. By applying the proposed communication-reduced method, we show that energy and computational cost of the nodes is also preserved.

Comprehensive analysis of the March 7, 2019 Somogyszob, Hungary earthquake cluster

2020 ◽  
Author(s):  
Zoltán Wéber ◽  
Barbara Czecze ◽  
Zoltán Gráczer ◽  
Bálint Süle ◽  
Gyöngyvér Szanyi ◽  
...  
Keyword(s):  
Cross Correlation ◽  
Main Shock ◽  
Moment Tensor ◽  
Thrust Fault ◽  
Comprehensive Analysis ◽  
Waveform Cross Correlation ◽  
Event Location ◽  
Earthquake Cluster ◽  
The Moment ◽  
Fault Mechanism

<div>A magnitude ML 4.0 earthquake struck southwest Hungary on March 7, 2019. The earthquake was reported to be felt in some 53 localities with maximum intensity V on the EMS scale. The earthquake was preceded by four foreshocks and followed by four aftershocks. The hypoDD solutions using differential travel times from waveform cross-correlation show significant improvements in event location. We were able to determine the moment tensor solutions for the main shock and one of the foreshocks and aftershocks, each representing thrust fault mechanism with a horizontal P-axis pointing towards N-NE. The obtained moment magnitudes range from Mw 1.5 to 3.8 with source radii between 100 and 500 m. The stress drop spans from 12 to 19 bars.</div><div> <div> <div> </div> </div> </div>

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