Yuki SuzukiKenji KawaiRobert J. GellerSatoru TanakaWeerachai SiripunvarapornSongkhun BoonchaisukSutthipong NoisagoolYasushi IshiharaTaewoon KimThe University of TokyoMahidol UniversityJapan Agency for Marine-Earth Science and TechnologyScience2020-08-252020-08-252020-10-01Physics of the Earth and Planetary Interiors. Vol.307, (2020)003192012-s2.0-85088871014https://repository.li.mahidol.ac.th/handle/123456789/57860© 2020 Elsevier B.V. Although previous tomographic studies found a large low S-velocity province (LLSVP) in the lowermost mantle beneath the Pacific, due to a lack of resolution it was unclear whether the LLSVP consists of clusters of small-scale low-velocity anomalies or large-scale anomalies. We recently deployed a seismic-array in Thailand which provides a dataset with wide azimuthal coverage of the western Pacific LLSVP. We analyze the new dataset using waveform inversion, and find high-velocity anomalies extending vertically to a height of ~400 km above the core-mantle boundary (CMB) beneath the Philippine Sea and small-scale low-velocity patches with a diameter of ~300 km at the CMB beneath New Guinea. The locations of the high-velocity anomalies are consistent with the past Izanagi-plate subduction boundary, and the low-velocity anomalies can be interpreted as a small-scale plume cluster. Hence we conclude that vertical flow (upwelling plumes and downwelling of slabs) is dominant in the lowermost mantle beneath the western Pacific region.Mahidol UniversityEarth and Planetary SciencesPhysics and AstronomyArticleSCOPUS10.1016/j.pepi.2020.106544