Rapid Earthquake Association and Location

2019 ◽  
Vol 90 (6) ◽  
pp. 2276-2284 ◽  
Author(s):  
Miao Zhang ◽  
William L. Ellsworth ◽  
Gregory C. Beroza
Keyword(s):  
Travel Time ◽  
Time Windows ◽  
Grid Point ◽  
Seismic Events ◽  
Relative Location ◽  
Central Apennines ◽  
Location Method ◽  
Event Location ◽  
Seismic Characterization ◽  
Location Methods

ABSTRACT Rapid association of seismic phases and event location are crucial for real‐time seismic monitoring. We propose a new method, named rapid earthquake association and location (REAL), for associating seismic phases and locating seismic events rapidly, simultaneously, and automatically. REAL combines the advantages of both pick‐based and waveform‐based detection and location methods. It associates arrivals of different seismic phases and locates seismic events primarily through counting the number of P and S picks and secondarily from travel‐time residuals. A group of picks are associated with a particular earthquake if there are enough picks within the theoretical travel‐time windows. The location is determined to be at the grid point with the most picks, and if multiple locations have the same maximum number of picks, the grid point among them with smallest travel‐time residuals. We refine seismic locations using a least‐squares location method (VELEST) and a high‐precision relative location method (hypoDD). REAL can be used for rapid seismic characterization due to its computational efficiency. As an example application, we apply REAL to earthquakes in the 2016 central Apennines, Italy, earthquake sequence occurring during a five‐day period in October 2016, midway in time between the two largest earthquakes. We associate and locate more than three times as many events (3341) as are in Italy's National Institute of Geophysics and Volcanology routine catalog (862). The spatial distribution of these relocated earthquakes shows a similar but more concentrated pattern relative to the cataloged events. Our study demonstrates that it is possible to characterize seismicity automatically and quickly using REAL and seismic picks.

Relocation of seismicity of the Pannonian Basin using the Bayesloc multiple event location algorithm between 1996 and 2019

2020 ◽  
Author(s):  
Barbara Czecze ◽  
István Bondár
Keyword(s):  
Pannonian Basin ◽  
Ground Truth ◽  
Velocity Model ◽  
Measure Data ◽  
Seismic Events ◽  
Seismicity Pattern ◽  
Statistical Framework ◽  
Event Location ◽  
Location Algorithm ◽  
Location Methods

<p>The objective of this work was to relocate the entire seismicity of the Pannonian Basin with the Bayesloc algorithm, a Markov-Chain Monte Carlo inversion scheme using a Bayesian statistical framework.</p><p><span>In the Hungarian National Seismological Bulletin the magnitudes and event locations are determined with the iLoc location algorithm using the 3D global RSTT velocity model, and we used these locations as initial coordinates. In our work, we have used all of the instrumentally registered seismic events between 1996 and 2019 in the Pannonian Basin.</span></p><p><span>During data preprocessing we used graph theory to measure data connectivity. Similar to all multiple-event location methods, Bayesloc performs better when events are recorded on a common network. </span></p><p><span>We used</span> <span>several hundreds</span> <span>of ground truth events (quarry blasts, mine explosions, earthquakes)</span> <span>to tie down</span> <span>the seismicity pattern to known ground truth locations by giving them tighter prior distributions.</span></p><p><span>Based on the day-time peak on the origin-hour distribution of the bulletin earthquakes we assume that there are anthropogenic events labeled as earthquakes in the catalog, therefore we created a „Suspected</span> <span>explosions (SX)” group to set prior constrains.</span></p><p><span>The results show that the events around the mines are dramatically better clustered. The prior constraints contributed remarkably to the outcome of the relocation. We show that the results present an improved view of the seismicity of the region.</span></p>

Relative location of microseismic events with multiple masters

Geophysics ◽  
2016 ◽  
Vol 81 (4) ◽  
pp. KS149-KS158 ◽  
Author(s):  
Vladimir Grechka ◽  
Zhao Li ◽  
Bo Howell
Keyword(s):  
Anisotropic Media ◽  
Gradual Decrease ◽  
Relative Location ◽  
Location Method ◽  
Location Errors ◽  
Satisfactory Performance ◽  
Microseismic Data ◽  
Event Location ◽  
Microseismic Events ◽  
Paraxial Ray

A recently proposed paraxial ray-based technique for relative location of microseismicity is extended to accommodate several master events with respect to which other events, termed the slaves, are located. The multi-master extension addresses two issues inherent for the existing single-master algorithm: a gradual decrease of its accuracy with the distance from the master and less than satisfactory performance in the presence of strong velocity heterogeneity. Those deficiencies are handled by applying an improved paraxial traveltime formula, exact in homogeneous elliptically anisotropic media, and by distributing masters in the subsurface to sample its heterogeneity. The contributions of different master events to the hypocenter of a given slave are automatically weighted to enhance the influence of adjacent masters, ensuring the precise slave location, and to suppress distant ones, tending to increase the slave-location errors. Tests of the multi-master relative event-location method on synthetic and field microseismic data demonstrate its precision and flexibility as well as applicability to both surface and downhole microseismic geometries.

scholarly journals Updates to the Regional Seismic Travel Time (RSTT) Model: 2. Path-dependent Travel-time Uncertainty

2021 ◽  
Vol 178 (2) ◽  
pp. 313-339
Author(s):  
Michael L. Begnaud ◽  
Dale N. Anderson ◽  
Stephen C. Myers ◽  
Brian Young ◽  
James R. Hipp ◽  
...  
Keyword(s):  
Travel Time ◽  
Random Effects ◽  
Mean Squared Error ◽  
Random Effects Model ◽  
Location Error ◽  
Crust And Upper Mantle ◽  
Time Uncertainty ◽  
Uncertainty Estimates ◽  
Event Location ◽  
Travel Time Uncertainty

AbstractThe regional seismic travel time (RSTT) model and software were developed to improve travel-time prediction accuracy by accounting for three-dimensional crust and upper mantle structure. Travel-time uncertainty estimates are used in the process of associating seismic phases to events and to accurately calculate location uncertainty bounds (i.e. event location error ellipses). We improve on the current distance-dependent uncertainty parameterization for RSTT using a random effects model to estimate slowness (inverse velocity) uncertainty as a mean squared error for each model parameter. The random effects model separates the error between observed slowness and model predicted slowness into bias and random components. The path-specific travel-time uncertainty is calculated by integrating these mean squared errors along a seismic-phase ray path. We demonstrate that event location error ellipses computed for a 90% coverage ellipse metric (used by the Comprehensive Nuclear-Test-Ban Treaty Organization International Data Centre (IDC)), and using the path-specific travel-time uncertainty approach, are more representative (median 82.5% ellipse percentage) of true location error than error ellipses computed using distance-dependent travel-time uncertainties (median 70.1%). We also demonstrate measurable improvement in location uncertainties using the RSTT method compared to the current station correction approach used at the IDC (median 74.3% coverage ellipse).

scholarly journals Analysis of Advantages and Disadvantages of the Location Methods of International Auricular Acupuncture Points

2016 ◽  
Vol 2016 ◽  
pp. 1-13 ◽  
Author(s):  
Pei-Jing Rong ◽  
Jing-Jun Zhao ◽  
Lei Wang ◽  
Li-Qun Zhou
Keyword(s):  
Research Quality ◽  
Auricular Acupuncture ◽  
Acupuncture Points ◽  
Location Method ◽  
International Standard ◽  
Advantages And Disadvantages ◽  
International Standardization ◽  
The Right ◽  
Auricular Therapy ◽  
Location Methods

The international standardization of auricular acupuncture points (AAPs) is an important basis for auricular therapy or auricular diagnosis and treatment. The study on the international standardization of AAPs has gone through a long process, in which the location method is one of the key research projects. There are different points of view in the field of AAPs among experts from different countries or regions. By only analyzing the nine representative location methods, this paper tried to offer a proper location method to locate AAPs. Through analysis of the pros and cons of each location method, the location method applied in the WFAS international standard of AAPs is thoroughly considered as an appropriate method. It is important to keep the right direction during developing an International Organization for Standardization (ISO) international standard of auricular acupuncture points and to improve the research quality of international standardization for AAPs.

Multi-itinerary optimization as cloud service

2021 ◽  
Vol 64 (11) ◽  
pp. 121-129
Author(s):  
Alexandru Cristian ◽  
Luke Marshall ◽  
Mihai Negrea ◽  
Flavius Stoichescu ◽  
Peiwei Cao ◽  
...  
Keyword(s):  
Travel Time ◽  
Time Windows ◽  
Algorithm Design ◽  
Cloud Service ◽  
Multiple Agents ◽  
Solution Quality ◽  
Traffic Conditions ◽  
Time Distance ◽  
And Performance ◽  
Vehicle Capacity

In this paper, we describe multi-itinerary optimization (MIO)---a novel Bing Maps service that automates the process of building itineraries for multiple agents while optimizing their routes to minimize travel time or distance. MIO can be used by organizations with a fleet of vehicles and drivers, mobile salesforce, or a team of personnel in the field, to maximize workforce efficiency. It supports a variety of constraints, such as service time windows, duration, priority, pickup and delivery dependencies, and vehicle capacity. MIO also considers traffic conditions between locations, resulting in algorithmic challenges at multiple levels (e.g., calculating time-dependent travel-time distance matrices at scale and scheduling services for multiple agents). To support an end-to-end cloud service with turnaround times of a few seconds, our algorithm design targets a sweet spot between accuracy and performance. Toward that end, we build a scalable approach based on the ALNS metaheuristic. Our experiments show that accounting for traffic significantly improves solution quality: MIO finds efficient routes that avoid late arrivals, whereas traffic-agnostic approaches result in a 15% increase in the combined travel time and the lateness of an arrival. Furthermore, our approach generates itineraries with substantially higher quality than a cutting-edge heuristic (LKH), with faster running times for large instances.

scholarly journals A Novel Single-Terminal Fault Location Method for AC Transmission Lines in a MMC-HVDC-Based AC/DC Hybrid System

Energies ◽  
2018 ◽  
Vol 11 (8) ◽  
pp. 2066 ◽  
Author(s):  
Shimin Xue ◽  
Junchi Lu ◽  
Chong Liu ◽  
Yabing Sun ◽  
Baibing Liu ◽  
...  
Keyword(s):  
Transmission Lines ◽  
Fault Location ◽  
Control Strategies ◽  
Linear Regression Analysis ◽  
Location Method ◽  
Fault Resistance ◽  
Ac Networks ◽  
Minimum Residual ◽  
Ac Transmission ◽  
Location Methods

Accurate and reliable fault location method for alternating current (AC) transmission lines is essential to the fault recovery. MMC-based converter brings exclusive non-linear characteristics to AC networks under single-phase-to-ground faults, thus influencing the performance of the fault location method. Fault characteristics are related to the control strategies of the converter. However, the existing fault location methods do not take the control strategies into account, with further study being required to solve this problem. The influence of the control strategies to the fault compound sequence network is analyzed in this paper first. Then, a unique boundary condition that the fault voltage and negative-sequence fault current merely meet the direct proportion linear relationship at the fault point, is derived. Based on these, a unary linear regression analysis is performed, and the fault can be located according to the minimum residual sum function principle. The effectiveness of the proposed method is verified by PSCAD/EMTDC simulation platform. A large number of simulation results are used to verify the advantages on sampling frequency, fault resistance, and fault distance. More importantly, it provides a higher ranging precision and has extensive applicability.

Nonstationary Bayesian kriging: A predictive technique to generate spatial corrections for seismic detection, location, and identification

1998 ◽  
Vol 88 (5) ◽  
pp. 1275-1288 ◽  
Author(s):  
Craig A. Schultz ◽  
Stephen C. Myers ◽  
James Hipp ◽  
Christopher J. Young
Keyword(s):  
Travel Time ◽  
Linear Prediction ◽  
A Priori ◽  
Bayesian Kriging ◽  
Coverage Criterion ◽  
Form Representation ◽  
Seismic Characterization ◽  
Variable Damping ◽  
Data Coverage ◽  
Prediction Techniques

Abstract Seismic characterization works to improve the detection, location, and identification of seismic events by correcting for inaccuracies in geophysical models. These inaccuracies are caused by inherent averaging in the model, and, as a result, exact data values cannot be directly recovered at a point in the model. Seismic characterization involves cataloging reference events so that inaccuracies in the model can be mapped at these points and true data values can be retained through a correction. Application of these corrections to a new event requires the accurate prediction of the correction value at a point that is near but not necessarily coincident with the reference events. Given that these reference events can be sparsely distributed geographically, both interpolation and extrapolation of corrections to the new point are required. In this study, we develop a closed-form representation of Bayesian kriging (linear prediction) that incorporates variable spatial damping. The result is a robust nonstationary algorithm for spatially interpolating geophysical corrections. This algorithm extends local trends when data coverage is good and allows for damping (blending) to an a priori background mean when data coverage is poor. Benchmark tests show that the technique gives reliable predictions of the correction value along with an appropriate uncertainty estimate. Tests with travel-time residual data demonstrate that combining variable damping with an azimuthal coverage criterion reduces the large errors that occur with more classical linear prediction techniques, especially when values are extrapolated in poor coverage regions. In the travel-time correction case, this technique generates both seismic corrections along with uncertainties and can properly incorporate model error in the final location estimate. Results favor the applicability of this nonstationary algorithm to other types of seismic corrections such as amplitude and attenuation measures.

scholarly journals A wavefront orientation method for precise numerical determination of tsunami travel time

2013 ◽  
Vol 13 (11) ◽  
pp. 2863-2870 ◽  
Author(s):  
I. V. Fine ◽  
R. E. Thomson
Keyword(s):  
Travel Time ◽  
Grid Point ◽  
Point Pattern ◽  
Numerical Determination ◽  
Computationally Efficient ◽  
Tsunami Travel Time ◽  
Orientation Method ◽  
Huygens Principle ◽  
Improved Accuracy

Abstract. We present a highly accurate and computationally efficient method (herein, the "wavefront orientation method") for determining the travel time of oceanic tsunamis. Based on Huygens' Principle, the method uses an eight-point grid-point pattern and the most recent information on the orientation of the advancing wavefront to determine the time for a tsunami to travel to a specific oceanic location. The method is shown to provide improved accuracy and reduced anisotropy compared with the conventional multiple grid-point method presently in widespread use.

Automated microseismic event location by amplitude stacking and semblance

Geophysics ◽  
2019 ◽  
Vol 84 (6) ◽  
pp. KS191-KS210 ◽  
Author(s):  
Chengwei Zhang ◽  
Wenxiao Qiao ◽  
Xiaohua Che ◽  
Junqiang Lu ◽  
Baiyong Men
Keyword(s):  
Body Waves ◽  
S Waves ◽  
Advantages And Disadvantages ◽  
Location Uncertainty ◽  
Event Location ◽  
Time Average ◽  
Microseismic Events ◽  
Location Methods ◽  
Microseismic Event Location ◽  
Microseismic Event

Without the need to pick the arrival times of P- and S-waves, migration-based location methods, such as semblance-based and amplitude-stacking-based location methods, are best applied to microseismic events. By comparing and analyzing the advantages and disadvantages of these two methods, we have developed a new location method using amplitude information and semblance. First, we use the two-point ray-tracing method to calculate the traveltime of body waves from the trial point to each receiver, which determines the time-window positions of the P- and S-waves on all traces. Then, we calculate the semblance of the waveforms and the amplitude stacking of the ratio between the short-time average and the long-time average is computed upon the original waveform over the windows. Finally, the semblance weighted by amplitude stacking is used to image the spatial location of the microseismic events. Using experimental and synthetic data considering different factors that may affect the location result (e.g., the signal-to-noise ratio of the waveforms, the scale of the observation array, and the horizontal and vertical distances from the source to fracture zones), we perform microseismic event location with all three methods. According to the source imaging results from experimental and synthetic tests, the semblance method has great location uncertainty in the radial direction but it has good constraints in the circumferential direction; the amplitude-stacking method exhibits the opposite result; and the weighted-semblance method has good constraints in the circumferential and radial directions because it inherits the advantages of semblance-based and amplitude-stacking-based methods. Therefore, compared with existing migration-based location methods, our weighted-semblance method indicates stronger stability and lower location uncertainty, even when downhole monitoring is conducted with a limited aperture of the receiver array.

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