Detection of tectonic and volcanic deformation as anomalies in InSAR:
deep-learning tailored to differential data
Abstract
There are now more interferograms being generated from global satellite
radar datasets than can be assessed by hand. The reliable, automatic
detection of true displacement from these data is therefore critical,
both for monitoring deformation related to geohazards and understanding
solid earth processes. We discuss improvements to an unsupervised, event
agnostic method for automatically detecting deformation in unwrapped
interferograms. We use an anomaly detection framework that recognises
any deformation as “anomalies” by learning the ‘typical’
spatio-temporal pattern of atmospheric and other noise in sequences of
interferograms. Here, we present developments to our prototype model,
ALADDIn (Autoencoder-LSTM based Anomaly Detector of Deformation in
InSAR) using (1) a self-attention training technique to exploit
redundancy in interferogram networks to capture the temporal structure
of signals and (2) the addition of synthetic data for training. We
evaluate the impact of these developments using two geophysical
scenarios: (1) the detection of the same M_w 5.7 earthquake used to
test our original model (20.03.2019, south-west Turkey), (2) the
persistent uplift of Domoyu volcano (17.05.2017 to 14.12.2018,
Argentina). We make a quantitative evaluation of the performance of our
method using synthetic test data and find that for peak displacements
exceeding a few cm and of length-scale greater than a few hundred
metres, overall detection accuracy is 80 to 90%.