Delaney Park Array - Anchorage, Alaska
USGS Article - Seismic Monitoring of the Atwood BuildingInteractive Map
Downtown Anchorage Alaska sits on top of the great Alaskan subduction zone and has been subjected to large damaging earthquakes in the past. The March 27th, 1964 (Good Friday), magnitude 9.2 great Alaska earthquake shook the ground for more than 4 minutes over a 50,000-square-mile region and caused 131 deaths. Photo 1 shows the Anchorage city skyline (left) and the recently instrumented Robert Atwood building as seen from Delaney Park (right), the site of the new ANSS geotechnical array.
Photo 1(a&b). The skyline of downtown Anchorage (left)and the Atwood building and Delaney Park geotechnical strong motion array (right).
Instrumentation
The Delaney Park Array, deployed to provide the input wavefield to the Atwood building, has 3-component accelerometers at 6 levels (Figure 1) within the near-surface soil column and also at the surface. A soft formation called the Bootlegger Cove, is thought to be responsible for much of the damage in downtown anchorage during the great 1964 earthquake. Blow counts are down in the single digits at depths of over 100 feet in this formation and wave velocity decreases with depth through this formation (Figure 2). The geotechnical array is deployed to both sample the ground motions within this formation and above and below it. Photos 2 through 5 show various steps in the geotechnical strong motion array installation process.
Data from the Delaney Park Array are telemetered in real-time from Anchorage to the USGS office in Menlo Park, CA and to the Alaska Seismic Network at the University of Alaska in Fairbanks.
Figure 1. Soil profile and Geotechnical Array Layout at the Delaney Park Array in downtown Anchorage, Alaska.
Figure 2. Shear wave velocity with depth in Downtown Anchorage.
Photo 2. Delaney Park Array after drilling of 6 boreholes. The instrumented Atwood building can be seen in the background.
Photo 3. Installing a 3-component accelerometer at the Delaney Park Geotechnical Strong Motion Array.
Photo 4. Using glass beads to couple the borehole accelerometer to the borehole casing.
Photo 5. The completed fenced in array and recording hut in October of 2003.
