An assessment of uncertainties in VS profiles obtained from microtremor observations in the phased 2018 COSMOS blind trials

Abstract Site response is a critical consideration when assessing earthquake hazards. characterization key to understanding site effects as influenced by seismic conditions of the local geology. Thus, number geophysical methods were developed meet demand for accurate and cost-effective results. As consequence, studies have been administered periodically blind trials evaluate state-of-practice on-site characterization. We present results from Consortium Organizations Strong Motion Observation Systems (COSMOS) trials, which used data recorded surface-based microtremor array (MAM) at four sites where geomorphic vary deep alluvial basins an alpine valley. Thirty-four invited analysts participated. Data incrementally released 17 available who participated in all phases: (1) two-station arrays, (2) sparse triangular (3) complex nested or circular (4) geological control information including drill hole data. Another set provided two phases only. Although one consisted recordings three-component sensors, other three only vertical-component sensors. The cover range noise source distributions, ranging with highly directional wave field others omni-directional (azimuthally distributed) fields. review different processing techniques (e.g., beam-forming, spatial autocorrelation, cross-correlation, interferometry) applied compare effectiveness between differing distributions. define M index quality based on estimates time-averaged shear-wave velocity upper 10 ( V S10 ), 30 S30 100 S100 300 S300 ) meters show its usefulness quantitative comparisons S profiles multiple analysts. Our findings are expected aid building evidence-based consensus preferred arrays methodology future effects.