Geochemistry, Geophysics, Geosystems
Supporting Information for
Spatio-temporal Variations of the Slow Slip Event between 2008 and 2013 in the
Southcentral Alaska Subduction Zone
Yuning Fu1, Zhen Liu1 and Jeffrey T. Freymueller2
1. Jet Propulsion Laboratory, California Institute of Technology, Pasadena, California, USA
2. Geophysical Institute, University of Alaska Fairbanks, Fairbanks, Alaska, USA
Contents of this file
Figures S1 and S2
Introduction
The supporting information includes two figures. Figure S1: the synthetic test results for
the time-dependent inversion strategy used in this study. We create synthetic slip in
space and time that are similar to the true slip location and history in the paper, and then
create the synthetic GPS time series with realistic noise (~3mm on horizontal and ~5mm
on the vertical) added. We apply the same time-dependent inversion approach to the
synthetic data. The results are shown in the supplementary figure S1. Our resolution test
shows that the SSEs in both Upper Cook Inlet and Lower Cook Inlet are well resolved in
space. The temporal variation is also well captured by the filter. The inverted peak slip
rate is less than the input one due to both spatial and temporal smoothing effects but
total moment is conserved. Figure S2: analysis of earthquake catalog for the
southcentral Alaska subduction zone at all depths. We plot earthquakes of the whole
area of southcentral Alaska subduction zone at all depths of this segment of the
subduction zone; the relationship between cumulative number of earthquakes (at every
depth) and magnitude; cumulative number of earthquakes for all magnitudes and
cumulative number of earthquakes with magnitude > 1.2.
1
Figure S1. a) Synthetic cumulative slip with two slip areas corresponding to Upper and
Lower Cook Inlet SSEs. b) Cumulative slip from time-dependent slip inversion. c) and d)
Estimated fault slip rate from a time-dependent inversion of the synthetic data (black)
with 1-sigma uncertainty (dashed line) versus input slip rate (red line) at the selected
patches A and B as indicated in a). Smoothing in the Kalman filter may cause a smaller
fault slip rate estimate on a given patch, but the correct total moment is recovered. Two
events are simulated with similar location and duration as the observed slip events. To
construct the synthetic time series, we added random walk noise with a process noise
sigma of 1.5mm/sqrt(yr) on all components, and Gaussian noise of ~3mm on the
horizontal and ~5mm on the vertical components.
2
Figure S2. (a) Earthquakes of the whole area of southcentral Alaska subduction zone at
all depths of this segment of the subduction zone. (b) Relationship between cumulative
number of earthquakes (at every depth) and magnitude. (c) Cumulative number of
earthquakes for all magnitudes. (d) Cumulative number of earthquakes with magnitude >
1.2.
3