Novel anisotropic teleseismic body-wave tomography code AniTomo to illuminate heterogeneous anisotropic upper mantle: Part II – Application to data of passive seismic experiment LAPNET in northern Fennoscandia

The passive seismic experiment AniMaLS was organized in 2017 in the Sudetes in Poland. One of the objectives was to study the anisotropy of the sub-crustal lithosphere and asthenosphere beneath the NE termination of the Bohemian Massif. Temporary seismic network of 23 broadband stations was operating in the area of Sudetes mountains and Fore-Sudetic Block, covering a ~200 x 100 km large area, with ~30 km spacing between stations. Obtained recordings were supplemented with data from permanent stations of Czech and Polish seismological networks located in the study area.The Sudetes belong to internal zone of Variscan Orogen and are located in the NE part of the Bohemian Massif, between the Elbe Fault in SW and the Odra Fault in NE. The sudetic lithosphere represents a complex mosaic of several units with distinct histories of tectonic evolution and with consolidation ages ranging from the upper Proterozoic to the Quaternary. The aim of the project is to study seismic structure and anisotropy of the lithosphere-asthenosphere system based on broadband seismograms of local, regional and teleseismic events. The obtained data will be analysed using several interpretation methods. The poster presents the results of analysis by shear wave splitting method.The analysis was done based on SKS and SKKS phases recorded during a ~2 years observation period. For analysis, three single-station methods were used: cross-correlation, eigenvalue minimization and transverse energy minimization. The dependence of resulting splitting parameters on the backazimuth of the event was also analysed. The results show that time delays between slow and fast S-wave components are typically in the range of ~0.5-1.6 sec, with average 1.2 sec. The splitting is interpreted as a result of lattice-preferred orientation (LPO) of mantle olivine. The azimuths of fast velocity axis are mostly consistent and showed largely WNW-ESE direction. They correlate well with trends of tectonic units observed at the surface and with strike directions of major fault zones. This suggests vertically coherent deformation throughout the lithosphere and frozen-in LPO, reflecting last tectonic episode which shaped Sudetic area. Obtained results were also compared with previous seismic studies of the upper mantle anisotropy in the neighboring areas by various methods.

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Upper mantle structure of the northeastern Arabian Platform from teleseismic body-wave tomography

Physics of The Earth and Planetary Interiors ◽

10.1016/j.pepi.2020.106549 ◽

2020 ◽

Vol 307 ◽

pp. 106549

Author(s):

Simone Pilia ◽

Hao Hu ◽

Mohammed Y. Ali ◽

Nicholas Rawlinson ◽

Aiguo Ruan

Keyword(s):

Upper Mantle ◽

Body Wave ◽

Mantle Structure ◽

Upper Mantle Structure ◽

Wave Tomography ◽

Arabian Platform

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Moment magnitude estimates for Central Anatolian earthquakes using coda waves

10.5194/se-2019-8 ◽

2019 ◽

Author(s):

Tuna Eken

Keyword(s):

Empirical Relation ◽

Active Regions ◽

Moment Magnitude ◽

Central Anatolia ◽

Coda Wave ◽

Seismic Experiment ◽

Tectonically Active ◽

Passive Seismic ◽

Passive Seismic Experiment ◽

Good Agreement

Abstract. Proper estimate of moment magnitude that is a physical measure of the energy released at earthquake source is essential for better seismic hazard assessments in tectonically active regions. Here a coda wave modeling approach that enables the source displacement spectrum modeling of examined event was used to estimate moment magnitude of central Anatolia earthquakes. To achieve this aim, three component waveforms of local earthquakes with magnitudes 2.0 ≤ ML ≤ 5.2 recorded at 72 seismic stations which have been operated between 2013 and 2015 within the framework of the CD-CAT passive seismic experiment. An inversion on the coda wave traces of each selected single event in our database was performed in five different frequency bands between 0.75 and 12 Hz. Our resultant moment magnitudes (MW-coda) exhibit a good agreement with routinely reported local magnitude (ML) estimates for study area. Finally, we present an empirical relation between MW-coda and ML for central Anatolian earthquakes.

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POLENET/LAPNET teleseismic P wave travel time tomography model of the upper mantle beneath northern Fennoscandia

Solid Earth ◽

10.5194/se-7-425-2016 ◽

2016 ◽

Vol 7 (2) ◽

pp. 425-439 ◽

Cited By ~ 7

Author(s):

Hanna Silvennoinen ◽

Elena Kozlovskaya ◽

Eduard Kissling

Keyword(s):

Upper Mantle ◽

Fennoscandian Shield ◽

P Wave ◽

Significant Feature ◽

Depth Range ◽

Low Velocity ◽

Lateral Velocity ◽

International Polar Year ◽

Northern Fennoscandia ◽

Wave Tomography

Abstract. The POLENET/LAPNET (Polar Earth Observing Network) broadband seismic network was deployed in northern Fennoscandia (Finland, Sweden, Norway, and Russia) during the third International Polar Year 2007–2009. The array consisted of roughly 60 seismic stations. In our study, we estimate the 3-D architecture of the upper mantle beneath the northern Fennoscandian Shield using high-resolution teleseismic P wave tomography. The P wave tomography method can complement previous studies in the area by efficiently mapping lateral velocity variations in the mantle. For this purpose 111 clearly recorded teleseismic events were selected and the data from the stations hand-picked and analysed. Our study reveals a highly heterogeneous lithospheric mantle beneath the northern Fennoscandian Shield though without any large high P wave velocity area that may indicate the presence of thick depleted lithospheric “keel”. The most significant feature seen in the velocity model is a large elongated negative velocity anomaly (up to −3.5 %) in depth range 100–150 km in the central part of our study area that can be followed down to a depth of 200 km in some local areas. This low-velocity area separates three high-velocity regions corresponding to the cratonic units forming the area.

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