Imaging evolution of Cascadia slow-slip event using high-rate GPS

This is a Preprint and has not been peer reviewed. The published version of this Preprint is available: This is version 1 of this Preprint.


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Yuji Itoh , Yosuke Aoki, Junichi Fukuda


The slip history of short-term slow slip event (SSE) is typically inferred from daily Global Positioning System (GPS) data, which, however, cannot image the sub-daily processes, leaving the underlying mechanisms of SSEs elusive. To address the temporal resolution issue, we attempted to employ the kinematic subdaily GPS analysis, which has never been applied to SSE studies because its signal-to-noise ratio has been believed too low. By carefully post-processing sub-daily positions to remove non-tectonic position fluctuation, our 30-minute kinematic data clearly exhibits the transient motion of a few mm during one Cascadia SSE. A spatiotemporal slip image by inverting the 30-minute data exhibits a multi-stage evolution; it consists of an isotropic growth of SSE followed by an along-strike migration and termination within the rheologically controlled down-dip width. This transition at the slip growth mode is similar to the rupture growth of regular earthquakes, implying the presence of common mechanical factors behind the two distinct slip phenomena. The comparison with a slip inversion of the daily GPS demonstrates the current performance and limitation of the subdaily data in the SSE detection and imaging.Better understanding of the non-tectonic noise in the kinematic GPS analysis will further improve the temporal resolution of SSE.



Earth Sciences, Geophysics and Seismology, Tectonics and Structure


GPS, GNSS, slow earthquake, SSE, slow slip, tremor, cascadia, kinematic GPS


Published: 2021-12-24 16:07


CC BY Attribution 4.0 International

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