Description: The Burmese arc consists of the Indo-Burman Ranges (IBR), an accretionary wedge in the west and the Central Myanmar Basin (CMB) in the east. It is bounded in the east by the seismically active Sagaing Fault to the Shan Plateau. Intermediate-depth seismicity below Myanmar occurs at depths up to ~150 km, generally understood to be related to the subducting Burma slab. We use ambient noise tomography to construct a regional three-dimension (3-D) shear wave velocity model, aiming at figuring out the transition from oceanic subduction to continental subduction/collision along the Burmese arc and how it affects the upper plate crustal deformation. Our dataset includes 30 seismic stations from a recently deployed temporary seismic array and ~50 permanent stations in and around Myanmar. Ambient noise corss-correlations are calculated at periods of 5-60 s and are inverted for a 3-D velocity model from the crust to the uppermost mantle. Our model shows a low-velocity anomaly extending to 〉20 km depths beneath the northern part of the CMB that accurately defines the Chindwin Subbasin. The crust beneath the IBM is characterized by low velocity, which probably reflects the fluid-rich accreted sediments that has experienced metamorphism in the mid-lower crust. Underneath the Sagaing Fault an N-S trending high-velocity anomaly is clearly visible at depths of 40-70 km in the uppermost mantle extending from 20°N to 24°N. The anomaly could represent a remnant slab of the Incertus Arc collision/subduction and mark the eastern boundary of the Burma plate.

Description: Using polarimetric radar observations, different microphysical characteristics were found in the asymmetric concentric eyewalls of Typhoon Lekima (2019). In addition to the differential reflectivity (ZDR) column, a typical size-sorting radar signature was evident in the upright inner eyewall: a cyclonically upwind offset of the ZDR maximum relative to the horizontal reflectivity (ZH) and specific differential phase (KDP) maxima. In contrast, the large values of ZDR were located just above the melting layer along the upper edge of the more tilted outer eyewall and did not extend downward to form a ZDR column. In the cyclonic direction, moreover, the large values of the three polarimetric variables in the outer eyewall almost overlapped, without the cyclonic offset of typical size-sorting radar signature. Thus, more active warm-cloud (cold-cloud) processes dominate in the outer (inner) eyewall, particularly for the production of large drops, closely associated with the intrinsic dynamical structure of the concentric eyewalls.