Siting Survey and Configuration Optimization of a New Regional Array in the Federal Republic of Germany
Abstract
This project is involved performing a siting survey for an advanced seismic array in the FRG which could be used in a multi-array network jointly with arrays in Scandinavia to detect and identify seismic events especially at regional distances. To assess the eventual capabilities of a new high-frequency array it was necessary not only to conduct a noise survey but also to determine signal coherence in an area corresponding to the array aperture. After an extensive field survey, the Bavarian Forest (BF) area was chosen as a target region to install a NORESS type array. The BF-area - as part of the Bohemian Massif - represents the largest outcropping crystalline complex in Central Europe. Detailed noise measurements show average values for the power spectrum slight lower than 1 nm-sq/Hz and a fairly smooth decay proportional to 1/f to the 4th power per decade up to 40 Hz, leading to a value of .0001 nm-sq/Hz to 10 Hz and .00001 nm-sq/Hz at 20 Hz. Diurnal variations due to industrial noise sources such as saw mills are mostly found in the 4 Hz to 10 Hz band. Compared to Scandinavia, the noise level in Central Europe is comparable or even lower for frequencies about 1 Hz but it is about a decade higher at 10 Hz and above. The spatial correlation properties of noise and signals were investigated with data from a temporary 9-element array with a diameter of 3 km. In the 1 Hz - 2 Hz band, the noise coherence values drop to 0.25 at interstation distances of 800 m, and in the 2 Hz - 4 Hz band at interstation distancies of 400 m, respectively. There is no clear evidence for a negative noise correlation distance at these frequencies.
Document Details
- Document Type
- Technical Report
- Publication Date
- Mar 15, 1990
- Accession Number
- ADA223486
Entities
People
- H. -p. Harjes