gCAPjoint, A Software Package for Full Moment Tensor Inversion of Moderately Strong Earthquakes with Local and Teleseismic Waveforms

2020 ◽  
Vol 91 (6) ◽  
pp. 3550-3562
Author(s):  
Qipeng Bai ◽  
Sidao Ni ◽  
Risheng Chu ◽  
Zhe Jia
Keyword(s):  
Software Package ◽  
Epicentral Distance ◽  
Joint Inversion ◽  
Moment Tensor ◽  
Centroid Moment Tensor ◽  
Waveform Data ◽  
Strong Earthquakes ◽  
Moment Tensors ◽  
Seismic Networks ◽  
Full Moment Tensor

Abstract Earthquake moment tensors and focal depths are crucial to assessing seismic hazards and studying active tectonic and volcanic processes. Although less powerful than strong earthquakes (M 7+), moderately strong earthquakes (M 5–6.5) occur more frequently and extensively, which can cause severe damages in populated areas. The inversion of moment tensors is usually affected by insufficient local waveform data (epicentral distance <5°) in sparse seismic networks. It would be necessary to combine local and teleseismic data (epicentral distance 30°–90°) for a joint inversion. In this study, we present the generalized cut-and-paste joint (gCAPjoint) algorithm to jointly invert full moment tensor and centroid depth with local and teleseismic broadband waveforms. To demonstrate the effectiveness and explore the limitations of this algorithm, we perform case studies on three earthquakes with different tectonic settings and source properties. Comparison of our results with global centroid moment tensor and other catalog solutions illustrates that both non-double-couple compositions of the focal mechanisms and centroid depths can be reliably recovered for very shallow (<10  km) earthquakes and intermediate-depth events with this software package.

scholarly journals Bayesian Inference of Centroid Moment Tensors of the 2019 Ambon (Mw 6.5) Aftershock Earthquake Sequence, Indonesia: A Preliminary Result

2021 ◽  
Vol 873 (1) ◽  
pp. 012022
Author(s):  
A W Baskara ◽  
D P Sahara ◽  
A D Nugraha ◽  
A Muhari ◽  
A A Rusdin ◽  
...  
Keyword(s):  
Moment Tensor ◽  
Strike Slip ◽  
Fault Reactivation ◽  
Model Parameters ◽  
The South ◽  
Centroid Moment Tensor ◽  
Waveform Data ◽  
Moment Tensors ◽  
The Impact ◽  
Dextral Strike Slip

Abstract The Ambon Mw 6.5 earthquake on September 26th, 2019, had contributed to give severe damages and significantly increased seismicity around Ambon Island and surrounding areas. Mainshock was followed by aftershocks with spatial distribution added to the impact of destructions in this region. We investigated aftershocks sequences to reveal the effect of mainshock toward the change in the in-situ stress field, including the possibility of the existing faults reactivation and the generation of aftershocks. We inferred centroid moment tensor (CMT) for significant aftershock events with Mw more than 4.0 using waveform data recorded from October 18th to December 15th, 2019. The aftershock focal mechanism was determined using the Bayesian full-waveform inversion code ISOLA-Obspy. This approach provides the uncertainty of the CMT model parameters. From ten CMT solution we had inferred in three seismic clusters, we found that majority of events have a strike-slip mechanism. Four events located on the south of the N-S trendings have a dextral strike-slip fault type, reflected the rupture of the mainshocks fault plane. Three events in the cluster of Ambon Island are dextral strike-slip, confirming the presence of the fault reactivation. Meanwhile, three CMT solutions in the north show the dextral strike-slip faulting and may belong to the mainshock main fault, connected with the cluster in the south.

scholarly journals Quick regional centroid moment tensor solutions for the Emilia 2012 (northern Italy) seismic sequence

2012 ◽  
Vol 55 (4) ◽  
Author(s):  
Silvia Pondrelli ◽  
Simone Salimbeni ◽  
Paolo Perfetti ◽  
Peter Danecek
Keyword(s):  
Moment Tensor ◽  
Mediterranean Area ◽  
Northern Italy ◽  
Seismic Sequence ◽  
Centroid Moment Tensor ◽  
Strong Earthquakes ◽  
Magnitude Range ◽  
The Mediterranean ◽  
Centroid Moment Tensor Solutions

<p>In May 2012, a seismic sequence struck the Emilia region (northern Italy). The mainshock, of Ml 5.9, occurred on May 20, 2012, at 02:03 UTC. This was preceded by a smaller Ml 4.1 foreshock some hours before (23:13 UTC on May 19, 2012) and followed by more than 2,500 earthquakes in the magnitude range from Ml 0.7 to 5.2. In addition, on May 29, 2012, three further strong earthquakes occurred, all with magnitude Ml ≥5.2: a Ml 5.8 earthquake in the morning (07:00 UTC), followed by two events within just 5 min of each other, one at 10:55 UTC (Ml 5.3) and the second at 11:00 UTC (Ml 5.2). For all of the Ml ≥4.0 earthquakes in Italy and for all of the Ml ≥4.5 in the Mediterranean area, an automatic procedure for the computation of a regional centroid moment tensor (RCMT) is triggered by an email alert. Within 1 h of the event, a manually revised quick RCMT (QRCMT) can be published on the website if the solution is considered stable. In particular, for the Emilia seismic sequence, 13 QRCMTs were determined and for three of them, those with M &gt;5.5, the automatically computed QRCMTs fitted the criteria for publication without manual revision. Using this seismic sequence as a test, we can then identify the magnitude threshold for automatic publication of our QRCMTs.</p>

The Global Centroid Moment Tensor Catalog: Heterogeneities and improvements

2021 ◽  
Author(s):  
Álvaro González
Keyword(s):  
Subduction Zones ◽  
Moment Tensor ◽  
Statistical Seismology ◽  
Centroid Moment Tensor ◽  
Moment Tensors ◽  
Global Database ◽  
Intermediate Period ◽  
Data Compilation ◽  
Forecast Models ◽  
The Moment

&lt;p&gt;Statistical seismology relies on earthquake catalogs as homogeneous and complete as possible. However, heterogeneities in earthquake data compilation and reporting are common and frequently are not adverted.&lt;/p&gt;&lt;p&gt;The Global Centroid Moment Tensor Catalog (www.globalcmt.org) is considered as the most homogeneous global database for large and moderate earthquakes occurred since 1976, and it has been used for developing and testing global and regional forecast models.&lt;/p&gt;&lt;p&gt;Changes in the method used for calculating the moment tensors (along with improvements in global seismological monitoring) define four eras in the catalog (1976, 1977-1985, 1986-2003 and 2004-present). Improvements are particularly stark since 2004, when intermediate-period surface waves started to be used for calculating the centroid solutions.&lt;/p&gt;&lt;p&gt;Fixed centroid depths, used when the solution for a free depth did not converge, have followed diverse criteria, depending on the era. Depth had to be fixed mainly for shallow earthquakes, so this issue is more common, e.g. in the shallow parts of subduction zones than in the deep ones. Until 2003, 53% of the centroids had depths calculated as a free parameter, compared to 78% since 2004.&lt;/p&gt;&lt;p&gt;Rake values have not been calculated homogenously either. Until 2003, the vertical-dip-slip components of the moment tensor were assumed as null when they could not be constrained by the inversion (for 3.3% of the earthquakes). This caused an excess of pure focal mechanisms: rakes of -90&amp;#176; (normal), 0&amp;#176; or &amp;#177;180&amp;#176; (strike-slip) or +90&amp;#176; (thrust). Even disregarding such events, rake histograms until 2003 and since 2004 are not equivalent to each other.&lt;/p&gt;&lt;p&gt;The magnitude of completeness (&lt;em&gt;M&lt;/em&gt;&lt;sub&gt;c&lt;/sub&gt;) of the catalog is analyzed here separately for each era. It clearly improved along time (average &lt;em&gt;M&lt;/em&gt;&lt;sub&gt;c&lt;/sub&gt; values being ~6.4 in 1976, ~5.7 in 1977-1985, ~5.4 in 1986-2003, and ~5.0 since 2004). Maps of &lt;em&gt;M&lt;/em&gt;&lt;sub&gt;c&lt;/sub&gt; for different eras show significant spatial variations.&lt;/p&gt;

Comparison of local kinematic rupture joint inversion approaches for tsunami early warning: Examples of the 2017-2020 Mw > 6.3 East Aegean earthquakes

2021 ◽  
Author(s):  
Malte Metz ◽  
Marius Isken ◽  
Rongjiang Wang ◽  
Torsten Dahm ◽  
Haluk Özener ◽  
...  
Keyword(s):  
Early Warning ◽  
Joint Inversion ◽  
Moment Tensor ◽  
Strong Motion ◽  
Aegean Sea ◽  
High Rate ◽  
Source Inversion ◽  
Dynamic Rupture ◽  
Centroid Moment Tensor ◽  
Tsunami Early Warning

&lt;p&gt;The fast inversion of reliable centroid moment tensor and kinematic rupture parameters of earthquakes occurring near coastal margins is a key for the assessment of the tsunamigenic potential and early tsunami warning (TEW). In recent years, more and more multi-channel seismic and geodetic online station networks have been built-up to improve the TEW, for instance the GNSS and strong motion networks in Italy, Greece, and Turkey, additionally to the broadband seismological monitoring. Inclusion of such data for the fast kinematic source inversion can improve the resolution and robustness of its&amp;#8217; solutions. However, methods have to be further developed and tested to fully exploit the potential of such rich joint dataset.&lt;/p&gt;&lt;p&gt;In this frame, we compare and test two in-house developed, kinematic / dynamic rupture inversion methods which are based on completely different approaches. The IDS (Iterative Deconvolution and Stacking, Zhang et al., 2014) combines an iterative seismic network inversion with back projection techniques to retrieve subfault source time functions. The pseudo dynamic rupture model (Dahm et al., in review) links the rupture front propagation estimate based on the Eikonal equation with the dislocation derived from a boundary element method to model dislocation snapshots. We used the latter in both a fast rupture estimate and a fully probabilistic source inversion.&lt;/p&gt;&lt;p&gt;We use some Mw &gt; 6.3 earthquakes that occurred in the coastal range of the Aegean Sea as an example for comparison: the Mw 6.3 Lesbos earthquake (12 June 2017), the Mw 6.6 Bodrum earthquake (20 July 2017), and the recent Mw 7.0 earthquake which occurred at Samos on 30 October 2020. The latter earthquake and the resulting tsunami caused fatalities and severe damage at the shorelines of Samos and around the city of Izmir, Turkey.&lt;br&gt;The fast estimates are based on only little data and/or prior information obtained from the regional seismicity catalogue and available active fault information. The large number of seismic (broadband, strong motion) and geodetic (high-rate GNSS) stations in local and regional distance from the earthquake with good azimuthal coverage jointly inverted with InSAR data allows for robust inversion results. These, and other solutions, are used as a reference for the comparison of our fast source estimates.&lt;br&gt;Preliminary results of the slip distribution and the source time function are in good agreement with modelling results from other authors.&lt;/p&gt;&lt;p&gt;We present our insights into the kinematics of the chosen earthquakes investigated by means of joint inversions. Finally, the accuracy of our first fast source estimates, which could be of potential use in tsunami early warning, will be discussed.&lt;/p&gt;

scholarly journals Source Parameter of Earthquakes in Talala, Gujarat (India): An Implication towards Seismotectonic

Proceedings ◽  
2019 ◽  
Vol 24 (1) ◽  
pp. 7
Author(s):  
Sandeep Kumar Aggarwal
Keyword(s):  
Epicentral Distance ◽  
Moment Tensor ◽  
Source Parameters ◽  
Focal Depth ◽  
B Value ◽  
Complete Sequence ◽  
P Value ◽  
Centroid Moment Tensor ◽  
North East ◽  
Lateral Plane

Talala is an excellent example of triggered neo-tectonic seismicity between two dams during a monsoon. An earthquake of Mmax 5.1 on 6 November 2007 at 21.16° N; 70.54° E, with a focal depth of 4.5 km and complete sequence, was first-time recorded on the latest broadband sensor. This found a dam/monsoon-induced earthquake preceded by 18 foreshocks of 2 ≤ Mw ≤ 4.8 within 9 h 11 minute, as well as smaller shocks that may not have been recorded because of sparse network coverage. After the deployment of local mobile observatories, aftershocks of Mw ≥ 1.0, which continued for months and subsided to background seismicity after four months, were recorded. The same kind of phenomena repeated, with Mmax 5.0 on 20 October 2011 at 21.06° N; 70.50° E, focal depth 5.5 km, which implies that the potential to generate dam/monsoon-induced seismicity took nearly four years again. These phenomena continued and the sequence was recorded by a network of 10 broadband seismographs (three in the Talala area and seven at an epicentral distance of 30 to 300 km). Centroid Moment Tensor (CMT) solutions and spectral source parameters of mainshock and aftershocks are evaluated to understand the seismotectonic of the region. The CMT depicts a major strike-slip motion along East North East-West South West with a left-lateral plane at 4.5 km depth. This indicates a sympathetic fault extension of the Son-Narmada fault. The source parameters of 400 shocks of Mw 1.0 to 5.1 found seismic moment 1011 to 1016.5 N-m, source radii 120–850 meter, and a stress drop of 0.003 to 25.43 Mpa. The b-value, p-value, fractal dimension, and slip on estimated different faults. The comparison between Talala and Koyna dam-induced source parameters tries to establish a comparison of seismicity from different parts of the world.

scholarly journals Seismic Moment Tensor Solutions from GeoNet Data to Provide a Moment Magnitude Scale for New Zealand

2021 ◽  
Author(s):  
◽  
Elizabeth de Joux Robertson
Keyword(s):  
New Zealand ◽  
Seismic Moment ◽  
Moment Tensor ◽  
Velocity Model ◽  
Moment Tensor Inversion ◽  
Moment Magnitude ◽  
Seismic Moment Tensor ◽  
Waveform Data ◽  
Moment Tensors ◽  
The Moment

<p>The aim of this project is to enable accurate earthquake magnitudes (moment magnitude, MW) to be calculated routinely and in near real-time for New Zealand earthquakes. This would be done by inversion of waveform data to obtain seismic moment tensors. Seismic moment tensors also provide information on fault-type. I use a well-established seismic moment tensor inversion method, the Time-Domain [seismic] Moment Tensor Inversion algorithm (TDMT_INVC) and apply it to GeoNet broadband waveform data to generate moment tensor solutions for New Zealand earthquakes. Some modifications to this software were made. A velocity model can now be automatically used to calculate Green's functions without having a pseudolayer boundary at the source depth. Green's functions can be calculated for multiple depths in a single step, and data are detrended and a suitable data window is selected. The seismic moment tensor solution that has either the maximum variance reduction or the maximum double-couple component is automatically selected for each depth. Seismic moment tensors were calculated for 24 New Zealand earthquakes from 2000 to 2005. The Global CMT project has calculated CMT solutions for 22 of these, and the Global CMT project solutions are compared to the solutions obtained in this project to test the accuracy of the solutions obtained using the TDMT_INVC code. The moment magnitude values are close to the Global CMT values for all earthquakes. The focal mechanisms could only be determined for a few of the earthquakes studied. The value of the moment magnitude appears to be less sensitive to the velocity model and earthquake location (epicentre and depth) than the focal mechanism. Distinguishing legitimate seismic signal from background seismic noise is likely to be the biggest problem in routine inversions.</p>

scholarly journals Local seismotectonic analysis of the July 2019 Molucca Sea earthquake sequence based on moment tensor solutions

2021 ◽  
Vol 8 (1) ◽  
Author(s):  
Aditya Dwi Prasetio ◽  
Mohammad Hasib ◽  
Andi Amran ◽  
Syuhada ◽  
Febty Febriani ◽  
...  
Keyword(s):  
Moment Tensor ◽  
Normal Fault ◽  
Earthquake Sequence ◽  
Tectonic Activity ◽  
Waveform Data ◽  
Moment Tensor Solution ◽  
Compressional Stress ◽  
Fault Mechanism ◽  
Sea Area ◽  
Full Moment Tensor

AbstractWe investigate the local seismotectonic of the Molucca Sea area using moment tensor calculations for the earthquakes that occurred in July 2019 at a depth of 10–55 km. The mainshock of Mw 6.8 occurred on July 7, followed by aftershocks until July 18, with magnitudes ranging from Mw 4.6 to Mw 5.8. Moment tensor solutions are calculated by applying Isolated Asperities (ISOLA) software using the full waveform data recorded at regional seismic stations. The analyzed frequency bands used in this study are 0.01–0.03 Hz and 0.04–0.05 Hz for the event with Mw ≥ 5 and Mw < 5, respectively. We provide validations of new moment tensor solutions for Mw < 5 events in the Molucca Sea region for the period during the earthquake sequence. The results show that thrust and oblique faults are dominant during this event, which indicate a compressional stress of divergent double subduction (DDS) of the Sangihe and Halmahera arcs. Only one full moment tensor solution reveals the normal fault mechanism, which may indicate the manifestation of strain release of compressional stress in the surrounding area. Furthermore, these results also support the previous studies suggesting that the Talaud-Mayu Ridge located in the middle of the Molucca Sea has developed as a consequence of the transpressional tectonic activity.

From National to Transnational Seismic Monitoring Products and Services in the Republic of Bulgaria, Republic of Moldova, Romania, and Ukraine

2021 ◽  
Author(s):  
Alexandru Mărmureanu ◽  
Constantin Ionescu ◽  
Bogdan Grecu ◽  
Dragos Toma-Danila ◽  
Alexandru Tiganescu ◽  
...  
Keyword(s):  
Risk Mitigation ◽  
Seismic Monitoring ◽  
Current Status ◽  
Waveform Data ◽  
Strong Earthquakes ◽  
Crustal Earthquakes ◽  
Seismic Waveform ◽  
The Republic ◽  
Seismic Networks ◽  
Research Facilities

Abstract The aim of this article is to analyze the background, current status, and outlook of seismic monitoring products and services in Bulgaria, Moldova, Romania, and Ukraine. These countries manage seismic networks that contribute to the European Integrated Data Archive node in the framework of the Observatories and Research Facilities for European Seismology, which represents a collaborative effort in coordinating observational seismology across the European region through the collection, archiving, and dissemination of seismic waveform data, metadata, and related products. All of the aforementioned countries share a common threat: strong earthquakes occurring in the Vrancea area located in central-eastern Romania at intermediate depths (usually in the 60–180 km interval). Events such as the ones on 10 November 1940 and 4 March 1977 generated high damage in Romania, northern Bulgaria, and Moldova. In addition to Vrancea, crustal earthquakes in areas such as Shabla or Dulovo can lead to cross-border damage. Therefore, understanding the way national seismic networks are distributed, how they cooperate, and the products and services that they provide in (near) real time and their terms is of significant interest in the context of necessary hazard harmonization and joint emergency intervention and risk mitigation actions.

Seismic Monitoring for High-Precision Delineation of Fault Geometry and Stress; Case Study for the West Texas Subscription Array

2020 ◽  
Author(s):  
Sepideh Karimi ◽  
Adam Baig ◽  
Aaron Booterbaugh ◽  
Yoones Vaezi ◽  
Mark Stacey ◽  
...  
Keyword(s):  
High Precision ◽  
Moment Tensor ◽  
Next Generation ◽  
Stress Regime ◽  
Moment Tensors ◽  
Wastewater Disposal ◽  
Delaware Basin ◽  
West Texas ◽  
Seismicity Monitoring ◽  
Seismic Networks

&lt;p&gt;Seismicity potentially induced through wastewater disposal, hydraulic fracture completion, or other industrial operations, has been a cause for increasing public concern over the last decade. Monitoring for this activity has focussed on the problems of location and characterization, often to a relatively rough degree of precision. Regulations typically spell out responses for operators should an event exceed a magnitude threshold within a specified distance of their facilities. While this type of monitoring is critical for ensuring injections be conducted effectively while minimizing potential damage from shaking and public alarm, it often leaves many unanswered questions in terms of the underlying processes.&lt;/p&gt;&lt;p&gt;Understanding these questions entails that we demand more out of the seismic networks, essentially upgrading the data products to a &amp;#8220;next generation&amp;#8221; level.&amp;#160; The data from the network needs to be used to provide a detailed understanding of critical geological structures and geomechanics of the study area. This goal is facilitated through both a densification of hardware and a higher order of event processing. High-precision locations delivered through relative relocation methodologies delineate slipping fault structures, often resolving previously unknown features. Moment tensor inversion processing also helps reveal the orientations of faults and provides information on stress in the region. The resolution of these structures provides critical insight into understanding how a field is reacting.&lt;/p&gt;&lt;p&gt;We illustrate the application of this &amp;#8220;next-generation&amp;#8221; seismicity monitoring system to the Delaware Basin in West Texas, where we have deployed a network of 25 broadband seismometers complementing monitoring from TexNet and other networks. Despite being an exceptionally challenging recording environment, by aggregating all of these data we obtain a high-resolution catalog of earthquake hypocenters delineating a number of fault features. Inverting the stresses from the moment tensors of the highest-quality events shows a dominantly normal stress regime and tangibly resolves a rotation of axes transitioning across the basin. We illustrate both the logistical and processing requirements necessary for timely delivery of results highlighting the dynamics of seismicity in an active study area.&lt;/p&gt;

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

&lt;p&gt;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.&lt;/p&gt;&lt;p&gt;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.&lt;/p&gt;&lt;p&gt;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.&lt;/p&gt;&lt;p&gt;Grond can be used to optimise simultaneously seismic waveforms, amplitude spectra, waveform features, phase picks, static displacements from InSAR and GNSS, and gravitational signals.&lt;/p&gt;&lt;p&gt;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).&lt;/p&gt;

Sign in / Sign up

Export Citation Format

Share Document