DAS synthetic dataset

Abstract

Deliverable D1.3 of the ACT DigiMon project is a synthetic microseismic distributed acoustic sensins (DAS) dataset. There are a number of possible uses for such a dataset; for example supporting the development and testing of DAS processing algorithms, testing the efficacy of different array geometries in detecting and characterising events, or simulating a field experiment to better understand observed processes. Given the large number of possible uses it was decided that rather than simply delivering a collection of files of synthetic seismic events, it would be more valuable to deliver a modelling framework from which synthetic data can be generated as the need arises, combined with a small example dataset of a few events to demonstrate the capabilities. DAS systems record seismic wavefields and ground motion due to their sensitivity to strain along the axis of the fibre. To understand the response of DAS it is necessary to understand (1) the seismic source, (2) the path effects and (3) the site and instrument effects. In this report we discuss the modelling of the first two contributions of the DAS response; the source and path effects. We simulate the resulting particle motion and strain at the fibre location, resulting from realistic microseismic sources in geological models representative of the North Sea. The third contribution; site and instrument effects, is contained in the transfer function, which describes the mathematical relationship between the wavefield properties at the cable location to the recorded DAS output. The form of the transfer function is a key unanswered question which will be addressed in Task 1.2 of the DigiMon project.