Crustal structure beneath northern Myanmar: preliminary results from ambient noise tomography

Abstract

<p>Adjoining the Eastern Himalayan Syntaxis, linking to the Indian slab indentation northward and Andaman slab subduction eastward, Myanmar is one of the most complicated and active tectonic regions in the world, and exposed to a high seismic hazard. The Burmese arc consists of the Indo-Burman Ranges (IBR), an accretionary wedge in the west and the Central Myanmar Basin in the east. It is bounded in the east by the seismically active Sagaing Fault to the Shan Plateau which is part of the Asian plate. Intermediate-depth seismicity below Myanmar occurs at depths up to ~150 km, generally understood to be related to the subducting Burma slab.  An important open question concerns the transition from oceanic subduction to continental subduction/collision along the Burmense arc. The transition is also thought to affect the upper plate crust. In this study, we collected ambient noise data set based on a temporary seismic array in Myanmar in order to constrain the variation of crustal structure. The station array includes 30 broadband stations from a temporary network (code 6C 2019-2021) at GEOFON data center. They were deployed by the German Research Centre for Geosciences (GFZ) and the Department of Meteorology and Hydrology of Myanmar (DMH) across the eastern IBR and Central Myanmar Basin in early 2019  with an average interstation distance of ~60 km and data are available to 2020 for most stations. We calculated the cross-correlations daily for all available station pairs through the NoisePy code and stacked further into yearly time-series. We measured Rayleigh wave group and phase velocity dispersions from cross-correlations by using the frequency-time analysis (FTAN) and calculated maps of phase dispersion. As a next step, we will construct a detailed crustal and upper mantle structure beneath Myanmar.</p>