In Situ Shear‐Wave Velocity Measurements at the Delaney Park Downhole Array, Anchorage, Alaska

Abstract

Many studies are ongoing within Alaska’s most populous city to understand better its unique seismogenic setting as well as its seismic hazard and risk. With its relative proximity to the Aleutian megathrust subduction zone and other earthquake sources, Anchorage has been subjected to regular earthquakes, including the 1964 Great Alaska earthquake. In 2004, a downhole array was installed near downtown Anchorage within the Bootlegger Cove Formation, which was responsible for much of the ground failure during the 1964 earthquake. This study provides new information regarding the downhole array and the dynamic soil properties found at the array site. Shearand compression-wave velocities were measured at the site. Evaluation of the transfer function of the new velocity model is compared with the measured response at the site. In addition, several comparisons are performed utilizing nearby historic cone penetration test (CPT) and standard penetration test (SPT) data measured during installation of the deepest accelerometer at the site. A significant improvement in the theoretical modeling of the site is achieved utilizing the new shear-wave velocity profile.