scholarly journals Initial-rupture fault, main-shock fault, and aftershock faults: Fault geometry and bends inferred from centroid moment tensor inversion of the 2005 west off Fukuoka prefecture earthquake

2006 ◽  
Vol 58 (1) ◽  
pp. 69-74 ◽  
Author(s):  
Yoshihiro Ito ◽  
Kazushige Obara ◽  
Tetsuya Takeda ◽  
Katsuhiko Shiomi ◽  
Takumi Matsumoto ◽  
...  
Keyword(s):  
Main Shock ◽  
Moment Tensor ◽  
Moment Tensor Inversion ◽  
Fault Geometry ◽  
Centroid Moment Tensor ◽  
Fukuoka Prefecture ◽  
Initial Rupture

scholarly journals Regional centroid moment tensor inversion of small to moderate earthquakes in the Alps using the dense AlpArray seismic network: challenges and seismotectonic insights

Solid Earth ◽  
2021 ◽  
Vol 12 (6) ◽  
pp. 1233-1257
Author(s):  
Gesa Maria Petersen ◽  
Simone Cesca ◽  
Sebastian Heimann ◽  
Peter Niemz ◽  
Torsten Dahm ◽  
...  
Keyword(s):  
Seismic Activity ◽  
Moment Tensor ◽  
Southern Alps ◽  
Moment Tensor Inversion ◽  
Seismic Network ◽  
Central Alps ◽  
Normal Faulting ◽  
Centroid Moment Tensor ◽  
Study Region ◽  
Northern Dinarides

Abstract. The Alpine mountains in central Europe are characterized by a heterogeneous crust accumulating different tectonic units and blocks in close proximity to sedimentary foreland basins. Centroid moment tensor inversion provides insight into the faulting mechanisms of earthquakes and related tectonic processes but is significantly aggravated in such an environment. Thanks to the dense AlpArray seismic network and our flexible bootstrap-based inversion tool Grond, we are able to test different setups with respect to the uncertainties of the obtained moment tensors and centroid locations. We evaluate the influence of frequency bands, azimuthal gaps, input data types, and distance ranges and study the occurrence and reliability of non-double-couple (DC) components. We infer that for most earthquakes (Mw≥3.3) a combination of time domain full waveforms and frequency domain amplitude spectra in a frequency band of 0.02–0.07 Hz is suitable. Relying on the results of our methodological tests, we perform deviatoric moment tensor (MT) inversions for events with Mw>3.0. Here, we present 75 solutions for earthquakes between January 2016 and December 2019 and analyze our results in the seismotectonic context of historical earthquakes, seismic activity of the last 3 decades, and GNSS deformation data. We study regions of comparably high seismic activity during the last decades, namely the Western Alps, the region around Lake Garda, and the eastern Southern Alps, as well as clusters further from the study region, i.e., in the northern Dinarides and the Apennines. Seismicity is particularly low in the Eastern Alps and in parts of the Central Alps. We apply a clustering algorithm to focal mechanisms, considering additional mechanisms from existing catalogs. Related to the N–S compressional regime, E–W-to-ENE–WSW-striking thrust faulting is mainly observed in the Friuli area in the eastern Southern Alps. Strike-slip faulting with a similarly oriented pressure axis is observed along the northern margin of the Central Alps and in the northern Dinarides. NW–SE-striking normal faulting is observed in the NW Alps, showing a similar strike direction to normal faulting earthquakes in the Apennines. Both our centroid depths and hypocentral depths in existing catalogs indicate that Alpine seismicity is predominantly very shallow; about 80 % of the studied events have depths shallower than 10 km.

scholarly journals Performance of regional distance centroid moment tensor inversion applied to the 2004 mid-Niigata prefecture earthquake, Japan

2006 ◽  
Vol 167 (3) ◽  
pp. 1317-1331 ◽  
Author(s):  
Yoshihiro Ito ◽  
Shoji Sekiguchi ◽  
Tomomi Okada ◽  
Ryou Honda ◽  
Kazushige Obara ◽  
...  
Keyword(s):  
Moment Tensor ◽  
Moment Tensor Inversion ◽  
Centroid Moment Tensor ◽  
Niigata Prefecture

scholarly journals The Italian Seismic Bulletin: strategies, revised pickings and locations of the central Italy seismic sequence

2016 ◽  
Vol 59 ◽  
Author(s):  
Alessandro Marchetti ◽  
Maria Grazia Ciaccio ◽  
Anna Nardi ◽  
Andrea Bono ◽  
Francesco Mariano Mele ◽  
...  
Keyword(s):  
Focal Mechanism ◽  
Main Shock ◽  
Moment Tensor ◽  
Central Italy ◽  
Seismic Sequence ◽  
Centroid Moment Tensor ◽  
Moment Tensors ◽  
Emergency Group ◽  
First Motion ◽  
New Procedures

<p>The central Italy seismic sequence, started with the Mw = 6.0 Amatrice earthquake on August 24th 2016, is the first significant one after the Italian Seismic Bulletin (BSI) changed its analysis strategies in 2015. These new strategies consist on the release of the BSI every four months, the review of the events with ML ≥ 1.5 and the priority on the review of events with ML ≥ 3.5. Furthermore, in the last year we improved the bulletin tools and made possible the analysis of all the stations whose data are stored in the European Integrated Data Archive (EIDA). The new procedures and software utilities allowed, during the first month of 2016 emergency, to integrate, in the Bulletin, the temporary stations installed by the emergency group SISMIKO, both in real–time transmission and in stand-alone recording. In the early days of the sequence many of the BSI analysts were engaged in the monitoring room shifts, nevertheless at the end of August all events occurred in those days with ML ≥ 4 were analyzed; the largest event recovered and localized is a ML = 4.5 event immediately following the main shock. In September 2016, 83 events with ML ≥ 3.5 were analyzed and re-checked, the number of pickings greatly improved. The focal mechanism of the main shock was evaluated using first motion polarities, and compared with the available Time Domain Moment Tensors and Regional Centroid Moment Tensor. The first eight hours of the day on August 24th, the most critical for the INGV surveillance room, were carefully analyzed: the number of located events increased from 133 to 408. The magnitude of completeness, after the analysis of the BSI, has dropped significantly from about 3.5 to 2.7. The mainshock focal mechanism and the relative locations of the first 8 hours’ aftershocks give clues on the initial fault activation. The seismic sequence in November 2016 is still ongoing; it included a mainshock of Mw = 6.5 on October 30th and 3 events of magnitude greater than 5.0 one on August 24th and two on October 26th.</p>

Bayesian ISOLA: new tool for automated centroid moment tensor inversion

2017 ◽  
Vol 210 (2) ◽  
pp. 693-705 ◽  
Author(s):  
Jiří Vackář ◽  
Jan Burjánek ◽  
František Gallovič ◽  
Jiří Zahradník ◽  
John Clinton
Keyword(s):  
Moment Tensor ◽  
Moment Tensor Inversion ◽  
Centroid Moment Tensor

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.

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