Single‐station automated detection of transient deformation in GPS time series with the relative strength index: A case study of Cascadian slow slip

Abstract

The discovery of slow‐slip events over the past decades has changed our understanding of tectonic hazards and the earthquake cycle. Proper geodetic characterization of slow‐slip events is necessary for studies of regional interseismic, coseismic and postseismic deformation, and miscalculations can affect our understanding of the regional stress field and tectonic hazard. Because of the proliferation of GPS data over the last two decades, an automated algorithm is required to analyze the signals and model the deformation on a station by station basis. Using the relative strength index (RSI), a financial momentum oscillator, we test the ability to detect events of various sizes and durations. We first determine the statistics of the RSI under different noise conditions and then use this information as the basis for the automated transient detection algorithm by testing different synthetic signals. We then apply the technique to daily GPS displacement time series from 213 stations along the Cascadia subduction zone to form a record of transient deformation between 2005 and 2016. Our estimates of the spatial extent, duration, and propagation of major episodic tremor and slip (ETS) events are consistent with previous studies. We use the automated detections to remodel the displacement time series and obtain transient deformation rates over the past decade and discuss the tectonic implications. Finally, we analyze the correlation between transient detections and tremor showing good agreement between the two at slab depths commonly associated with ETS events.

Monitoring of the spatio-temporal change in the interplate coupling at northeastern Japan subduction zone based on the spatial gradients of surface velocity field

“…Ohtani et al 2010;Holt & Shcherbenko 2013;Crowell et al 2016). Ohtani et al (2010) and Holt & Shcherbenko (2013) focused to the horizontal strain rate field to find transient deformation events and determine their locations, while Crowell et al (2016) analysed 3-D displacement time-series at station by station to detect episodic tremor and slip events automatically.…”

“…Ohtani et al 2010;Holt & Shcherbenko 2013;Crowell et al 2016). Ohtani et al (2010) and Holt & Shcherbenko (2013) focused to the horizontal strain rate field to find transient deformation events and determine their locations, while Crowell et al (2016) analysed 3-D displacement time-series at station by station to detect episodic tremor and slip events automatically. However, Ohtani et al (2010) and Holt & Shcherbenko (2013) did not involve vertical displacement rates in their analysis even though Ohtani et al (2010) mentioned the extensibility of their method to include the vertical component.…”

Coseismic displacements on Ischia island, real-time GPS positioning constraints on earthquake source location

“…In literature, so far, the focus is mainly on the advantages of the GPS data in recovering large earthquake parameters, but recently there is a growing interest in developing automated algorithms for real-time determinations of seismological parameters and deformation analysis for smaller seismic events [Melgar et al, 2015;Crowell et al, 2016]. The real-time monitoring of ground deformations is not a technically demanding effort because of the broad spreading of GPS data, but may be extremely useful for assessing seismic location estimates, or for cross-checking purposes with other geophysical data in the early emergency phase.…”

Greedy Automatic Signal Decomposition and Its Application to Daily GPS Time Series

“…An ongoing aim of the tectonic GPS research community is to be able to both extract and detect transient motion in the GPS (see Lohman & Murray, ). Algorithmic transient detection aims to identify periods in time during which there occurs an acceleration and sustained velocity that is statistically distinct from the background (expected) velocity (e.g., Crowell et al, ). Accordingly, we do not suggest that GrAtSiD is detecting transient motion.…”