Microseismicity and active tectonics of the Fonualei Rift and Spreading Center.

Cremanns, Maximilian, Schmid, Florian , Kopp, Heidrun and Lange, Dietrich (2019) Microseismicity and active tectonics of the Fonualei Rift and Spreading Center. Open Access [Poster] In: AG Seismologie Jahrestagung 2019. , 24.-26.09.2019, Rastatt, Germany .

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The Lau basin is an active back arc system with several spreading centres and microplates rapidly evolving in time. In the northeast basin, we observe a complex setting of a back arc rifting system and a volcanic arc. The Fonualei Rift and Spreading Center (FRSC) is a part of this complex setting, striking northwest and accommodating eastwest extension between the Niuafo'ou microplate and the Tonga plate. The volcanic arc strikes northeast southwest, in order to this striking direction the Fonualei Rift offset to the volcanic arc decreases to the south. This results in an minimal offset off 10-15km to the active volcanic arc. The interplay of the FRSC and the Tofua volcanic arc are not fully understood. Therefor we want to use the microseismicity as a tool to understand these active tectonics. One goal was to record seismicity data and create an event catalogue.

We deployed a network of 16 ocean bottom seismometers (OBS) across the FRSC which recorded approximately 750 local events within a time span of 31 days. The events were located with the NonLinLoc (Non-Linear Location) software package. Further more we determined local and moment magnitudes.

The seismicity catalogue shows an average event rate of 24 events per day. The events are focused beneath the network and in a region south of the network. Especially in the southern region we recognised a highly increased event rate depending on time and locality. In a time span of 6 days we observed 600 events resulting in a event rate of up to 100 events per day. This high event rate is an indicator for an earthquake swarm. For the magnitudes frequency distribution we determined a b-value for the entire catalogue of 1.05 with a magnitude of completeness of 1.0.

With this microseismicity we were able to create an event catalogue which can be used as a starting point for more investigation within this region. For example we will analyse the focal mechanisms of selected events which will allow insights to the tectonics of the region.

Document Type: Conference or Workshop Item (Poster)
Dewey Decimal Classification: 500 Natural Sciences and Mathematics > 550 Earth sciences & geology
Subjects: Course of study: MSc Geophyscis
Research affiliation: OceanRep > GEOMAR > FB4 Dynamics of the Ocean Floor > FB4-GDY Marine Geodynamics
Kiel University
Date Deposited: 06 Jan 2020 14:53
Last Modified: 06 Jan 2020 14:53
URI: http://oceanrep.geomar.de/id/eprint/48431

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