Mathematical theory of acoustic emission and moment tensor solution.

Abstract We present regional earthquake magnitude conversion relations among different magnitude scales (Mw, Ms, mb, ML, and MD) for the Himalayan seismic belt developed from data of local, regional, and international seismological agencies (International Seismological Centre [ISC], National Earthquake Information Centre [NEIC], Global Centroid Moment Tensor Solution [CMT], International Data Centre [IDC], China Earthquake Administration [BJI], and National Centre for Seismology [NDI]). The intra- (within the same magnitude scale) and inter- (with different magnitude scales) magnitude regression relations have been established using the general orthogonal regression and orthogonal distance regression techniques. Results show that the intra-magnitude relations for Mw, Ms, and mb reported by the Global CMT, ISC, and NEIC exhibit 1:1 relationships, whereas ML reported by the IDC, BJI, and NDI deviates from this relationship. The IDC underestimates Ms and mb compared with the ISC, NEIC, and Global CMT; this may be due to different measurement procedures adopted by the IDC agency. The inter-magnitude relations are established between Mw,Global CMT and Ms, mb, and ML reported by the ISC, NEIC, IDC, and NDI, and compared with the previously developed regional and global regression relations. The duration (MD) and local (ML) magnitudes reported by NDI exhibit a 1:1 relationship. The derived magnitude regression relations are expected to support the homogenization of the earthquake catalogs and to improve seismic hazard assessment in this region.

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Neogene and active brittle deformation on Amorgos Island (Greece)

10.5194/egusphere-egu2020-10755 ◽

2020 ◽

Author(s):

Jan Behrmann ◽

Jakob Schneider ◽

Benjamin Zitzow

Keyword(s):

Moment Tensor ◽

Spatial Relationship ◽

Shear Zones ◽

Fault System ◽

Normal Faults ◽

Small Scale ◽

Past Century ◽

Fault Plane Solutions ◽

Moment Tensor Solution ◽

Late Neogene

<p>Amorgos is the south-eastern outpost of the Cyclades Islands in the Aegean Sea, which forms part of the Neogene-Quaternary zone of crustal and lithospheric N-S upper plate extension northward of the Hellenic subduction zone and deep sea trench. Apart from subduction-related earthquakes further south, the southern Aegean is affected by frequent earthquakes sourced in the upper plate. The twin earthquakes of 9 July 1956, followed by a strong tsunami, were the strongest events of this kind in the past Century. Hypocenters are related to a NE-SW oriented normal fault bounding the Amorgos-Santorini Graben System. There are questions in the literature regarding the seismic source and fault plane solutions, especially the contribution of a transcurrent faulting component.</p><p>We have analyzed the kinematics of brittle faults exposed on Amorgos Island itself that could be related to Neogene and active extensional and/or transcurrent deformation. Seismic slip often occurs on previously existing faults. Thus, their orientations and kinematics may help shed light on the structure of seismic sources at depth. We present evidence for a complex history of faulting. Early normal detachment faults and shear zones overprint older (rare) reverse faults, and are themselves overprinted by several sets of dominantly dextral NE and SE trending strike slip faults. Youngest is a conjugate set of NE trending high-angle normal faults. These are especially frequent along the SE coast of the island, suggesting a clear spatial relationship with the 1956 rupture. They can be fitted to a moment tensor solution similar to the published solutions for the 1956 Amorgos earthquake. The kinematic solution for the population of early normal faults suggests that the whole of Amorgos Island may have experienced a 15&#176; NNW tilt during later extension, which lets us suspect that the island could be a tilted block of a much larger fault system. Regarding long-term late Neogene to Quaternary kinematics, dextrally transtensive fault slip is required to fit the regional pattern of extensional deformation in the Aegean, and this is reflected by small-scale brittle faulting on Amorgos.</p>

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Discussion on moment tensor solution and seismogenic structure of Ruichang-Yangxin earthquake on 10 September 2011

Earthquake Science ◽

10.1007/s11589-012-0848-0 ◽

2012 ◽

Vol 25 (3) ◽

pp. 229-234

Author(s):

Lifen Zhang ◽

Guichun Wei ◽

Wulin Liao

Keyword(s):

Moment Tensor ◽

Seismogenic Structure ◽

Moment Tensor Solution

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Characterisation of fault plane and coseismic slip for the May 2, 2020, Mw 6.6 Cretan Passage earthquake from tide-gauge tsunami data and moment tensor solutions

10.5194/nhess-2021-183 ◽

2021 ◽

Author(s):

Enrico Baglione ◽

Stefano Lorito ◽

Alessio Piatanesi ◽

Fabrizio Romano ◽

Roberto Basili ◽

...

Keyword(s):

Tide Gauge ◽

Moment Tensor ◽

Early Warning Systems ◽

Thrust Fault ◽

Coseismic Slip ◽

Moment Tensor Solution ◽

Crete Island ◽

Tsunami Forecasting ◽

Oblique Convergence ◽

Splay Fault

Abstract. We present a source solution for the tsunami generated by the Mw 6.6 earthquake that occurred on May 2, 2020, about 807thinsp;km offshore south of Crete, in the Cretan Passage, on the shallow portion of the Hellenic Arc Subduction Zone (HASZ). The tide-gauges recorded this local tsunami on the southern coast of Crete island and Kasos island. We used these tsunami observations to constrain the geometry and orientation of the causative fault, the rupture mechanism and the slip amount. We first modelled an ensemble of synthetic tsunami waveforms at the tide-gauge locations, produced for a range of earthquake parameter values as constrained by some of the available moment tensor solutions. We allow for both a splay and a back-thrust fault, corresponding to the two nodal planes of the moment tensor solution. We then measured the misfit between the synthetic and the observed marigrams for each source parameter set. Our results identify the shallow steeply-dipping back-thrust fault as the one producing the lowest misfit to the tsunami data. However, a rupture on a lower angle fault, possibly a splay fault, with a sinistral component due to the oblique convergence on this segment of the HASZ, cannot be completely ruled out. This earthquake reminds us that the uncertainty regarding potential earthquake mechanisms at a specific location remains quite significant. In this case, for example, it is not possible to anticipate if the next event will be one occurring on the subduction interface, on a splay fault, or on a back-thrust which seems the most likely for the event under investigation. This circumstance bears important consequences because back-thrust and splay faults might enhance the tsunamigenic potential with respect to the subduction interface due to their steeper dip. Then, these results are relevant for tsunami forecasting both in the framework of the long-term hazard assessment and of the early warning systems.

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

Geoscience Letters ◽

10.1186/s40562-021-00200-z ◽

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.

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