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Abstract Urban basin investigation is crucial for seismic hazard assessment and mitigation. Recent advances in robust nodal‐type sensors facilitate the deployment of large‐N arrays in urban areas for high‐resolution basin imaging. However, arrays typically operate for only one month due to the instruments' battery life, and hence, only record a few teleseismic events. This limits the number of available teleseismic events for traditional receiver function (RF) analysis‐the primary method used in sediment‐basement interface imaging in passive source seismology. Insufficient stacking of RFs from a limited number of earthquakes could, however, introduce significant biases to the results. In this study, we present a novel Bayesian array‐based Coherent Receiver Function (CRF) method that can leverage datasets from short‐term dense arrays to constrain basin geometry. We cast the RF deconvolution as a sparsity‐promoted inverse problem, in which the deconvolution at a single‐station involves the constraints from neighboring stations and multiple events. We solve the inverse problem using a trans‐dimensional Markov chain Monte Carlo Bayesian algorithm to find an ensemble of RF solutions, which provides a quantitative way of deciding which features are well resolved and warrant geological interpretation. An application in the northern Los Angeles basin demonstrates the ability of our method to produce reliable and easy‐to‐interpret RF images. The use of dense seismic networks and the state‐of‐the‐art Bayesian array‐based CRF method can provide a robust approach for subsurface structure imaging. 

Myanmar is surrounded by complex seismotectonic elements and threatened by a high seismic risk. The Central yanmar Basin (CMB) hosts the largest and fastest growing cities of Myanmar. The CMB is bounded by the Indo- Myanmar subduction zone to the west and the Sagaing fault to the east and is a seismically active tectonic block that has experienced large earthquakes (up to magnitude 8.0). A large earthquake in this region would affect Yangon and its surrounding population of around 8 million. Sedimentary basins have a significant contribution to seismic wave propagation, amplification and duration of ground shaking. Thus, to more accurately estimate the seismic hazard, a clear understanding of the detailed basin structures is required. The goal of our study is to map crustal structures, i.e. crustal thickness, crustal blocks, basin shape, size and depth, fault geometry, dipping layers and intra-crustal layers beneath the Yangon region. We will present receiver functions from a dense array of 168 nodal seismometers with the goal of revealing high-resolution seismic images of the basin. Our dense array will improve basin imaging by reducing uncertainties in receiver function interpretations. Developing a better understanding of basin structures will help our understanding of seismic amplification in the basin and thus will help to more accurately estimate the seismic hazard of this region. 

Recent GPS studies show that the Indo-Burma subduction system is locked with the implication of a potential large-magnitude earthquake. To inform better seismic hazard models in the region, we need an improved understanding of the crustal structure and the dynamics of the Indo-Burma subduction system. The Bangladesh-India-Myanmar (BIMA) tripartite project deployed 60 broadband seismometers across the subduction system and have been continuously recording data for ~2 years. In this study, we computed receiver functions from 30 high-quality earthquakes (M≥5.9) with epicentral distances between 30º and 90º recorded by the array. The algorithm utilized ensures the uniqueness of the seismic model and provides an uncertainty estimate of every converted wave amplitude. We stacked all the receiver functions produced at each station along the entire transect to generate a cross-sectional model of the average crustal structure. The level of detail in the image is improved by computing higher frequency receiver functions up to 4 Hz. The results represent some of the strongest constraints on crustal structure across the subduction system. Beneath the Neogene accretionary prism's outer belt, we observe a primary conversion associated with the Ganges Brahmaputra Delta that ranges in depth from ~10 km near the deformation front up to ~12 km at the eastern boundary. From the eastern end of the Neogene accretionary prism to the Sagaing Fault, we image the Indian subducting slab and the Central Myanmar basin. The depth-extent of seismicity associated with the Wadati-Benioff zone is consistent with the locations of primary conversions from the subducting plate. We further verify the converted phases of the slab by analyzing azimuthal moveout variations. The Central Myanmar basin is roughly bowl-shaped in cross-section with a maximum thickness of ~15 km about halfway between the Kabaw and Sagaing faults. The average crustal thickness beneath the Ganges-Brahmaputra delta is ~20 km, most likely representing a transitional crust formed from thinning of the continental crust intruded and underplated by igneous rocks. In contrast, the average thickness of the continental crust beneath the Central Myanmar basin is ~40 km. Our results provide a baseline model for future geophysical investigations of the Indo-Burma subduction zone. 

The seismology component of this experiment will consist of a 2.5 dimensional transect that will cross from Bangladesh into Myanmar. We will install as many stations as possible on hard rock sites to minimize noise, although this will not be possible in low-lying deltaic areas. The array will consist of three lines. The middle line will be closely spaced in order to image shallow crustal features. It will have a station spacing of 5-10 km in Bangladesh expanding to 15 km in eastern Myanmar. To image the detachment megathrust at 10-20 km depth in the accretionary prism, a 100-km-long section spanning the Bangladesh and India border will have station spacing of 5 km or less. Two flanking lines located ~40 km on either side will have ~40 km spacing. This 80 km wide swath is critical for earthquake locations and body- and surface-wave tomography. The stations will operate for ~2 years, providing ample recordings from a wide backazimuth distribution of local, regional, and teleseismic events, and ambient noise for analysis