Seismic Monitoring for Rockfall at Yucca Mountain: Concept Tests Barbara Luke 1 , Kristi Twilley 1 , Helena Murvosh 2 , Ramzi El-Khater 3 , Jin Cheng 1 , Evangelos Yfantis 2 , David Harris 4 1 Engineering Geophysics Laboratory, and Department of Civil and Environmental Engineering, University of Nevada Las Vegas 2 Branagan & Associates, Inc. 3 Computer Graphics and Image Processing Laboratory, and School of Computer Science, University of Nevada Las Vegas 4 Lawrence Livermore National Laboratory Abstract For the purpose of proof-testing a system intended to remotely monitor rockfall inside a potential radioactive waste repository at Yucca Mountain, a system of seismic sub-arrays will be deployed and tested on the surface of the mountain. The goal is to identify and locate rockfall events remotely using automated data collecting and processing techniques. We will install seismometers on the ground surface, generate seismic energy to simulate rockfall in underground space beneath the array, and interpret the surface response to discriminate and locate the event. Data will be analyzed using matched-field processing, a generalized beamforming method for localizing discrete signals. Software is being developed to facilitate the processing. To date, a three-component sub-array has been installed and successfully tested. Introduction The Engineering Geophysics Laboratory at University of Nevada Las Vegas (UNLV) is in the process of deploying, calibrating, and testing a passive seismic array on the surface at Yucca Mountain, the site of a proposed repository for high-level nuclear waste. The purpose of the array is to remotely monitor repository opening stability during construction and waste emplacement, and beyond. The primary goal is to assess the structural integrity of the emplacement drifts by identifying and localizing rockfalls that could compromise drift access, hinder waste retrievability, and potentially reduce the effective life of waste canisters. Collateral benefits of the proposed work include the ability to address some outstanding uncertainties regarding seismic wave attenuation in the vicinity of the repository and provision of a tool for security monitoring of the repository, to guard against unauthorized access and entry. Advantages of using remote monitoring include cost effectiveness, reduced risk of instrumentation failure due to heat