Contact of the Samoan plume with the Tonga subduction from intermediate and deep-focus earthquakes

0547282 - GFÚ 2022 RIV NL eng J - Journal Article
Hrubcová, Pavla - Vavryčuk, Václav
Contact of the Samoan plume with the Tonga subduction from intermediate and deep-focus earthquakes.
Surveys in Geophysics. Roč. 42, č. 6 (2021), s. 1347-1375. ISSN 0169-3298. E-ISSN 1573-0956
R&D Projects: GA ČR(CZ) GA17-19297S; GA ČR(CZ) GA19-06422S
Institutional support: RVO:67985530
Keywords : Tonga slab * Samoa plume * intermediate and deep earthquakes * velocity anomalies
OECD category: Volcanology
Impact factor: 7.965, year: 2021
Method of publishing: Open access
https://link.springer.com/article/10.1007%2Fs10712-021-09679-9

The Tonga subduction zone in the south-west Pacific is the fastest convergent plate boundary in the world with the most active mantle seismicity. This zone shows unique tectonic features including Samoan volcanic lineament of plume-driven origin near the northern rim of the Tonga subducting slab. The proximity of the Samoa hotspot to the slab is enigmatic and invokes debates on interactions between the Samoa plume and the Tonga subduction. Based on long-term observations of intermediate and deep-focus Tonga earthquakes reported in the Global Centroid Moment Tensor (CMT) catalog, we provide novel detailed imaging of this region. Accurate traveltime residua of the P- and S-waves recorded at two nearby seismic stations of the Global Seismographic Network are inverted for the P- and S-wave velocities and their ratio and reveal their pronounced lateral variations. In particular, they differ for the southern and northern parts of the Tonga subduction region. While no distinct anomalies are detected in the southern Tonga segment, striking low-velocity anomalies associated with a high V-p/V-s ratio are observed in the northern Tonga segment close to the Samoa plume. These anomalies spread through the whole upper mantle down to depths of similar to 600 km. Together with the fast extension of the northern back-arc Lau Basin, slab deformation and geochemical enrichment in the northern Tonga region, they trace deep-seated magmatic processes and evidence an interaction of the Tonga subduction with the Samoa plume.
Permanent Link: http://hdl.handle.net/11104/0323553