Path Calibration of the Democratic People’s Republic of Korea 3 September 2017 Nuclear Test

2021 ◽  
Author(s):  
Douglas S. Dreger ◽  
Roland Gritto ◽  
Owen Nelson
Keyword(s):  
Moment Tensor ◽  
Source Parameters ◽  
Seismic Source ◽  
Nuclear Test ◽  
Republic Of Korea ◽  
Source Analysis ◽  
The Sea Of Japan ◽  
Source Modeling ◽  
Velocity Models ◽  
Cross Correlation Analysis

Abstract The recovery of seismic source parameters requires the use of calibrated velocity models. Although at long periods it is possible to use relatively simple plane-layered models, calibration is still needed to better constrain source parameters. For the Democratic People’s Republic of Korea (DPRK) nuclear tests, this is particularly true when considering the use of seismic stations in Japan where paths cross the Sea of Japan. In this study, we perform forward waveform modeling to calibrate velocity structures. We show that we can arrive at a set of models that minimizes Rayleigh group-velocity anomaly at stations located in China, South Korea, and Japan. Overall moment tensor capability with the new models is improved such that cross-correlation analysis of the 20–50 s period waveforms recovers the true time alignment of the data, enabling better automated source analysis. We performed source-type inversions for the moment tensor jointly for long-period regional waveforms and regional and teleseismic P-waves polarity data for the latest and largest DPRK nuclear test and examine event discrimination/screening capability, scalar moment, and yield estimates with uncertainty. We present the models for improved seismic source modeling of the region.

scholarly journals The waveform inversion of mainshock and aftershock data of the 2006 M6.3 Yogyakarta earthquake

2021 ◽  
Vol 8 (1) ◽  
Author(s):  
Hijrah Saputra ◽  
Wahyudi Wahyudi ◽  
Iman Suardi ◽  
Ade Anggraini ◽  
Wiwit Suryanto
Keyword(s):  
Joint Inversion ◽  
Body Wave ◽  
Moment Tensor ◽  
Near Field ◽  
Source Parameters ◽  
Waveform Inversion ◽  
Moment Tensor Inversion ◽  
Slip Distribution ◽  
Aftershock Distribution ◽  
Velocity Models

AbstractThis study comprehensively investigates the source mechanisms associated with the mainshock and aftershocks of the Mw = 6.3 Yogyakarta earthquake which occurred on May 27, 2006. The process involved using moment tensor inversion to determine the fault plane parameters and joint inversion which were further applied to understand the spatial and temporal slip distributions during the earthquake. Moreover, coseismal slip distribution was overlaid with the relocated aftershock distribution to determine the stress field variations around the tectonic area. Meanwhile, the moment tensor inversion made use of near-field data and its Green’s function was calculated using the extended reflectivity method while the joint inversion used near-field and teleseismic body wave data which were computed using the Kikuchi and Kanamori methods. These data were filtered through a trial-and-error method using a bandpass filter with frequency pairs and velocity models from several previous studies. Furthermore, the Akaike Bayesian Information Criterion (ABIC) method was applied to obtain more stable inversion results and different fault types were discovered. Strike–slip and dip-normal were recorded for the mainshock and similar types were recorded for the 8th aftershock while the 9th and 16th June were strike slips. However, the fault slip distribution from the joint inversion showed two asperities. The maximum slip was 0.78 m with the first asperity observed at 10 km south/north of the mainshock hypocenter. The source parameters discovered include total seismic moment M0 = 0.4311E + 19 (Nm) or Mw = 6.4 with a depth of 12 km and a duration of 28 s. The slip distribution overlaid with the aftershock distribution showed the tendency of the aftershock to occur around the asperities zone while a normal oblique focus mechanism was found using the joint inversion.

scholarly journals Fully probabilistic seismic source inversion – Part 1: Efficient parameterisation

2013 ◽  
Vol 5 (2) ◽  
pp. 1125-1162 ◽  
Author(s):  
S. C. Stähler ◽  
K. Sigloch
Keyword(s):  
Moment Tensor ◽  
Source Parameters ◽  
Practical Importance ◽  
Principal Component ◽  
Seismic Source ◽  
Empirical Orthogonal Functions ◽  
Time Function ◽  
Source Inversion ◽  
Source Time Function ◽  
Earthquake Parameters

Abstract. Seismic source inversion is a non-linear problem in seismology where not just the earthquake parameters themselves, but also estimates of their uncertainties are of great practical importance. Probabilistic source inversion (Bayesian inference) is very adapted to this challenge, provided that the parameter space can be chosen small enough to make Bayesian sampling computationally feasible. We propose a framework for PRobabilistic Inference of Source Mechanisms (PRISM) that parameterises and samples earthquake depth, moment tensor, and source time function efficiently by using information from previous non-Bayesian inversions. The source time function is expressed as a weighted sum of a small number of empirical orthogonal functions, which were derived from a catalogue of >1000 STFs by a principal component analysis. We use a likelihood model based on the cross-correlation misfit between observed and predicted waveforms. The resulting ensemble of solutions provides full uncertainty and covariance information for the source parameters, and permits to propagate these source uncertainties into travel time estimates used for seismic tomography. The computational effort is such that routine, global estimation of earthquake mechanisms and source time functions from teleseismic broadband waveforms is feasible.

Waveform inversion for microseismic velocity analysis and event location in VTI media

Geophysics ◽  
2017 ◽  
Vol 82 (4) ◽  
pp. WA95-WA103 ◽  
Author(s):  
Oscar Jarillo Michel ◽  
Ilya Tsvankin
Keyword(s):  
Moment Tensor ◽  
Source Parameters ◽  
Waveform Inversion ◽  
Transversely Isotropic ◽  
Velocity Analysis ◽  
Origin Time ◽  
Velocity Models ◽  
Trade Offs ◽  
Receiver Array ◽  
Event Location

Waveform inversion (WI), which has been extensively used in reflection seismology, could provide improved velocity models and event locations for microseismic surveys. Here, we develop an elastic WI algorithm for anisotropic media designed to estimate the 2D velocity field along with the source parameters (location, origin time, and moment tensor) from microseismic data. The gradient of the objective function is obtained with the adjoint-state method, which requires just two modeling simulations at each iteration. In the current implementation the source coordinates and velocity parameters are estimated sequentially at each stage of the inversion to minimize trade-offs and improve the convergence. Synthetic examples illustrate the accuracy of the inversion for layered VTI (transversely isotropic with a vertical symmetry axis) media, as well as the sensitivity of the velocity-analysis results to noise, the length of the receiver array, errors in the initial model, and variability in the moment tensor of the recorded events.

Large Isotropic Component in the Source Mechanism of the 2013 Democratic People’s Republic of Korea Nuclear Test Revealed via a Hierarchical Bayesian Inversion

2020 ◽  
Vol 110 (1) ◽  
pp. 166-177 ◽  
Author(s):  
Marija Mustać ◽  
Babak Hejrani ◽  
Hrvoje Tkalčić ◽  
Seongryong Kim ◽  
Sang-Jun Lee ◽  
...  
Keyword(s):  
Moment Tensor ◽  
Nuclear Test ◽  
Republic Of Korea ◽  
Noise Model ◽  
Seismic Moment Tensor ◽  
Hierarchical Bayesian ◽  
Waveform Data ◽  
Isotropic Component ◽  
Recorded Data ◽  
Nuclear Tests

ABSTRACT The 12 February 2013 nuclear test conducted by the Democratic People’s Republic of Korea stands out among other nuclear tests because it produced unusually large transversal motions. Previous studies found various percentages of isotropic components of the seismic moment tensor (MT), which opens up an important question about the reliability of the methods and assumptions we routinely use to recover the seismic MT in the point source approximation. Of particular interest is the data noise model that can be utilized to represent the uncertainty associated with the recorded data. If the noise is not accounted for, this may result in a range of unwanted effects such as overfitting waveform data, and, in turn, it may lead to erroneous conclusions. We thus scrutinize the analyses of the seismic MT of this explosion by performing a thorough analysis of the source depth and time utilizing newly developed Earth structure models to invert seismograms at regional distances at different frequency bands. In addition, we estimate the solution uncertainty within a hierarchical Bayesian framework that allows accounting for noise in the data. Our results show that the resulting MT of this event contains an expectedly large isotropic component (about 70%) and a dip-slip faulting.

A user-friendly probabilistic earthquake source inversion framework for joint inversion of seismic, geodetic, and gravitational signals - The Grond toolkit

2020 ◽  
Author(s):  
Sebastian Heimann ◽  
Marius Isken ◽  
Daniela Kühn ◽  
Hannes Vasyura-Bathke ◽  
Henriette Sudhaus ◽  
...  
Keyword(s):  
Open Source ◽  
Joint Inversion ◽  
Moment Tensor ◽  
Source Parameters ◽  
Seismic Source ◽  
Magma Ascent ◽  
Caldera Collapse ◽  
Waveform Data ◽  
Trade Offs ◽  
Finite Fault

<p>Seismic source and moment tensor waveform inversion is often ill-posed or non-unique if station coverage is poor or signals are weak. Three key ingredients can help in these situations: (1) probabilistic inference and global search of the full model space, (2) joint optimisation with datasets yielding complementary information, and (3) robust source parameterisation or additional source constraints. These demands lead to vast technical challenges, on the performance of forward modelling, on the optimisation algorithms, as well as on visualisation, optimisation configuration, and management of the datasets. Implementing a high amount of automation is inevitable.</p><p>To tackle all these challenges, we are developing a sophisticated new seismic source optimisation framework, Grond. With its innovative Bayesian bootstrap optimiser, it is able to efficiently explore large model spaces, the trade-offs and the uncertainties of source parameters. The program is highly flexible with respect to the adaption to specific source problems, the design of objective functions, and the diversity of empirical datasets.</p><p>It uses an integrated, robust waveform data processing, and allows for interactive visual inspection of many aspects of the optimisation problem, including visualisation of the result uncertainties. Grond has been applied to CMT moment tensor and finite-fault optimisations at all scales, to nuclear explosions, to a meteorite atmospheric explosion, and to volcano-tectonic processes during caldera collapse and magma ascent. Hundreds of seismic events can be handled in parallel given a single optimisation setup.</p><p>Grond can be used to optimise simultaneously seismic waveforms, amplitude spectra, waveform features, phase picks, static displacements from InSAR and GNSS, and gravitational signals.</p><p>Grond is developed as an open-source package and community effort. It builds on and integrates with other established open-source packages, like Kite (for InSAR) and Pyrocko (for seismology).</p>

scholarly journals Fully probabilistic seismic source inversion – Part 1: Efficient parameterisation

Solid Earth ◽  
2014 ◽  
Vol 5 (2) ◽  
pp. 1055-1069 ◽  
Author(s):  
S. C. Stähler ◽  
K. Sigloch
Keyword(s):  
Moment Tensor ◽  
Source Parameters ◽  
Practical Importance ◽  
Principal Component ◽  
Seismic Source ◽  
Empirical Orthogonal Functions ◽  
Time Function ◽  
Source Inversion ◽  
Source Time Function ◽  
Earthquake Parameters

Abstract. Seismic source inversion is a non-linear problem in seismology where not just the earthquake parameters themselves but also estimates of their uncertainties are of great practical importance. Probabilistic source inversion (Bayesian inference) is very adapted to this challenge, provided that the parameter space can be chosen small enough to make Bayesian sampling computationally feasible. We propose a framework for PRobabilistic Inference of Seismic source Mechanisms (PRISM) that parameterises and samples earthquake depth, moment tensor, and source time function efficiently by using information from previous non-Bayesian inversions. The source time function is expressed as a weighted sum of a small number of empirical orthogonal functions, which were derived from a catalogue of >1000 source time functions (STFs) by a principal component analysis. We use a likelihood model based on the cross-correlation misfit between observed and predicted waveforms. The resulting ensemble of solutions provides full uncertainty and covariance information for the source parameters, and permits propagating these source uncertainties into travel time estimates used for seismic tomography. The computational effort is such that routine, global estimation of earthquake mechanisms and source time functions from teleseismic broadband waveforms is feasible.

scholarly journals The waveform inversion of mainshock and aftershock data of the 2006 M6.3 Yogyakarta earthquake

2021 ◽  
Author(s):  
Hijrah Saputra ◽  
Wahyudi Wahyudi ◽  
Iman Suardi ◽  
Ade Anggraini ◽  
Wiwit Suryanto
Keyword(s):  
Joint Inversion ◽  
Body Wave ◽  
Moment Tensor ◽  
Near Field ◽  
Source Parameters ◽  
Moment Tensor Inversion ◽  
Slip Distribution ◽  
Coseismic Slip ◽  
Aftershock Distribution ◽  
Velocity Models

Abstract This study comprehensively investigates the source mechanisms associated with the mainshock and aftershocks of the Yogyakarta earthquake of magnitude Mw = 6.3 on May 27, 2006. Therefore, this study is to provide a more precise answer to the controversial source mechanism. This study uses moment tensor inversion to obtain fault plane parameters and joint inversion to obtain spatial and temporal slip distributions during an earthquake. The coseismic slip distribution is overlaid with the relocated aftershock distribution to see the stress field variations around the tectonic area of the study. Moment tensor inversion uses near-field data, and joint inversion uses near-field and teleseismic body wave data. The data is filtered by trial and error using a bandpass filter with frequency pairs and velocity models from several previous studies. The green's function for moment tensor inversion calculated using the extended reflectivity method and joint inversion computed using the Kikuchi and Kanamori methods. In this study, we apply the Akaike Bayesian Information Criterion (ABIC) method to obtain more stable inversion results. The results of the mainshock and aftershock moment tensor inversion show different fault types. The mainshock fault types are strike-slip and dip-normal types, while the 8th aftershock is of the same type as the mainshock, while the 9th and 16th June are strike slips. The joint inversion results show two asperities. The maximum slip is 0.78 m, with the first asperity 10 km south of the mainshock and the second asperity 10 km north of the mainshock. The obtained source parameters are total seismic moment M0 = 0.4311E + 19 (Nm) or Mw = 6.4, with a source depth of 12 km and a source duration of 28 seconds. Slip distribution overlay with aftershock distribution shows compatibility. The type of focus mechanism that results from this joint inversion is the oblique.

Seismic Source Processes of 25 Earthquakes (Mw>5) in the Gulf of California

2022 ◽  
Author(s):  
Eduardo Huesca-Pérez ◽  
Edahí Gutierrez-Reyes ◽  
Luis Quintanar
Keyword(s):  
Gulf Of California ◽  
Moment Tensor ◽  
Source Parameters ◽  
Seismic Source ◽  
Focal Mechanisms ◽  
Process Models ◽  
Moment Tensors ◽  
Time Space ◽  
Double Couple ◽  
Broadband Seismograms

ABSTRACT The Gulf of California (GoC) is a complex tectonic boundary that has been instrumented in the past several decades to record broadband seismograms. This volume of data has allowed us to study several source parameters systematically. Before, only a few source parameters of earthquakes greater than magnitude five had been studied in the GoC area. We re-examined the focal mechanisms of several earthquakes in the southern GoC that occurred over the last 20 yr using local–regional distance broadband seismograms. These focal mechanisms were then used as input data to retrieve the time–space history of the rupture for each earthquake. This work contributes to the study of 25 rupture-process models computed with the method proposed by Yagi et al. (1999). To investigate more about the nature of the seismicity in the GoC, we also calculated the non-double-couple component of moment tensors for 45 earthquakes. Previous studies (e.g., Ortega et al., 2013, 2016) have shown that non-double-couple components from moment tensors in this region are associated with complex faulting, suggesting that oblique faults or several parallel faults are interacting simultaneously. Our results show that, at least for moderate earthquakes (5 < M < 6), rupture processes in the GoC show a complex interaction between fault systems. It is revealed on the important contribution of non-double-couple component obtained in the full moment tensor analysis.

scholarly journals Assessment of glacial-earthquake source parameters

2017 ◽  
Vol 63 (241) ◽  
pp. 867-876 ◽  
Author(s):  
STEPHEN A. VEITCH ◽  
MEREDITH NETTLES
Keyword(s):  
Source Parameters ◽  
Seismic Source ◽  
Earthquake Source ◽  
Source Modeling ◽  
Front Position ◽  
Earthquake Source Parameters ◽  
Slow Earthquakes ◽  
Earthquake Force ◽  
Single Force ◽  
Remote Sensing Techniques

ABSTRACTGlacial earthquakes are slow earthquakes of magnitude M~5 associated with major calving events at near-grounded marine-terminating glaciers. These globally detectable earthquakes provide information on the grounding state of outlet glaciers and the timing of large calving events. Seismic source modeling of glacial earthquakes provides information on the size and orientation of forces associated with calving events. We compare force orientations estimated using a centroid-single-force technique with the calving-front orientations of the source glaciers at or near the time of earthquake occurrence. We consider earthquakes recorded at four glaciers in Greenland – Kangerdlugssuaq Glacier, Helheim Glacier, Kong Oscar Glacier, and Jakobshavn Isbræ – between 1999 and 2010. We find that the estimated earthquake force orientations accurately represent the orientation of the calving front at the time of the earthquake, and that seismogenic calving events are produced by a preferred section of the calving front, which may change with time. We also find that estimated earthquake locations vary in a manner consistent with changes in calving-front position, though with large scatter. We conclude that changes in glacial-earthquake source parameters reflect true changes in the geometry of the source glaciers, providing a means for identifying changes in glacier geometry and dynamics that complements traditional remote-sensing techniques.

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