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- Title
Contribution of hydroacoustic data to long-term seismicity studies along then northern MAR.
- Authors
Giusti, Marion; Perrot, Julie; Maia, Marcia; Sukhovich, Alexey; Dziak, Robert; Luis, Joaquim; Cannat, Mathilde; Royer, Jean-Yves
- Abstract
The seismicity of the northern Atlantic Ocean, surrounded the MoMAR area has beenrecorded successively by the MARCHE array from 2005-2008 and the HYDROMOMARarray from 2010 to 2011 and from 2012 to 2014 (32˚ to 39˚ N). These arrays are composedof autonomous underwater hydrophones moored within the SOFAR channel on the flanksof the Mid-Atlantic Ridge (MAR). The low attenuation properties of the SOFARchannel for earthquake T-wave propagation result in a detection threshold reductionfrom a magnitude completeness level (Mc) of ∼4 for MAR events recorded by theland-based seismic networks to Mc=2.3 using these hydrophone arrays. 14715 eventswere located and constitute a 6-year catalog of seismicity around the MoMARarea. At large scales, seismicity rates show high values between the Pico and Oceanographerdiscontinuities mainly at segments presenting a symmetric mode of accretion wheremagmatic processes are dominant (Dziak et al., 2004; Giusti et al., 2018). On the contrary,from the Oceanographer to the Atlantis transform faults, the high seismicity rates are relatedto the asymmetric mode of accretion associated with detachment faults (Escartín et al.,2008). This seismicity rate difference traduces a difference in the mantle dynamics, probablydue to the vicinity of the Azores hot spot. The spatial distribution of the numbers of eventsper 50 km length of MAR enables us to determine the south limit of the hotspot at 35˚ 40’N. A cluster analysis were performed and we characterised the processes that generate theseclusters in terms of swarms (magmatic episode) or in terms of sequences (tectonic episode).No tectonic sequence reflecting a detachment fault mechanism is identified in the northernpart of the hydrophone array and swarms are mainly generated in symmetric or indeterminateareas. For the moment, we are not able to conclude about a seismic cycle in this area asthese hydrophone arrays recorded continuously during three years only. Teleseismicdata with the ISC catalog offer a great period of observations (∼50 years) but itis still unsufficient to define a recurrence of the processes around the MoMARarea. This study illustrates the potential of hydrophone data to monitor segment-scale ridgeprocesses in the MoMAR area. The HYDROMOMAR project will end in 2020 and willpermit us to build a 8 consecutive year catalog, that may allow us to better characterise theseismic cycle and confirm these preliminary observations. - Dziak, R. P., Smith, D. K., Bohnenstiehl, D. R., Fox, C. G., Desbruyeres, D.,Matsumoto, H. & Fornari, D. J. (2004). Evidence of a recent magma dike intrusion atthe slow spreading Lucky Strike segment, Mid-Atlantic Ridge. J. Geophys. Res.,109. - Escartín, J., Smith, D. K., Cann, J., Schouten, H., Langmuir, C. H., & Escrig, S. (2008).Central role of detachment faults in accretion of slow-spreading oceanic lithosphere. Nature,455(7214), 790. - Giusti, M., Perrot, J., Dziak, R. P., Sukhovich, A., and Maia, M. (2018). The august2010 ear- thquake swarm at north famous-famous segments, mid-atlantic ridge : Geophysicalevi- dence of dike intrusion. Geophys. J. Int.
- Subjects
MID-Atlantic Ridge; SEISMIC networks; LITHOSPHERE; GEOLOGIC hot spots; EARTHQUAKE zones; SONAR; MID-ocean ridges; OCEANOGRAPHERS; WENCHUAN Earthquake, China, 2008
- Publication
Geophysical Research Abstracts, 2019, Vol 21, p1
- ISSN
1029-7006
- Publication type
Article