This document summarizes research on visualizing seismic waves and permanent displacements from the 2011 Tohoku earthquake in Japan using GPS data. Dense GPS arrays in Japan captured both the seismic waves passing through as well as the permanent surface displacements of over 1 meter caused by the earthquake. Preliminary analysis of the GPS data shows the actual fault slip occurred over a 2 minute period and distinguishes between fast-moving seismic body and surface waves and the static permanent displacement.

1. Visualization of the seismic waves and permanent
displacements
Ronni Grapenthin1 The ARIA Team2
Jeffrey Freymueller1
1 Geophysical Institute, Univ. of Alaska Fairbanks
2 Susan Owen, Jet Propulsion Laboratory
Angelyn Moore, Jet Propulsion Laboratory
Frank Webb, Jet Propulsion Laboratory
Mark Simons, Caltech
April 10, 2011
Grapenthin et al. (UAF–GI) April 10, 2011 1 / 10

2. Tectonic Setting
Pacific plate moves
westward and collides with
Japan (Okhotsk Plate),
subducts underneath
this plate interaction drives
earthquakes offshore
Japan
Figure: USGS, http://earthquake.usgs.gov/earthquakes/world/japan/031111_M9.0prelim_geodetic_slip.php
Grapenthin et al. (UAF–GI) April 10, 2011 2 / 10

3. Background
For some background on plate mechanics, watch the following video
made available through the Education and Outreach Program of
IRIS (www.iris.edu/educate).
Grapenthin et al. (UAF–GI) April 10, 2011 3 / 10

4. Japan GEONET: Dense continuous GPS array
started in 1993 by
Geospatial Information
Authority (GSI) of Japan
with about 210 sites)
1995 Kobe earthquake
tragedy resulted in
intensified earthquake
research
see Sagiya (2004) for
more details
today: more than 1200
continuous GPS stations
Grapenthin et al. (UAF–GI) April 10, 2011 4 / 10

5. Permanent deformation measured by GPS
130 135 140 145
ARIA Preliminary Post and Coseismic
45 Displacements from Mw9.0 Sendai-Oki Earthquake 45
40 40 arrows show permanent
horizontal displacements
red: Mw 9.0 event at
05:46:23 UTC
35 35 blue: mainly Mw 7.9
event near Tokyo at
1m 06:26:12 UTC
1m
30 30
Figure shows horizontal displacements based on ARIA verion 0.3 position estimates for
GEONET stations. Coseismic displacement is shown in red, and first 8 hours of postseismic
motion is shown in blue, including motion caused by aftershocks. Bars at end of vector show
95% error estimate. Solutions courtesy of ARIA team at JPL and Caltech (email
aria@jpl.nasa.gov or aria@caltech.edu). All original GEONET RINEX data provided to Caltech by
theGrapenthin et al. (UAF–GI)
Geospatial Information Authority (GSI) of Japan. April 10, 2011 5 / 10

6. The displacement field at 5:50 UTC is the sum of . . .
Grapenthin et al. (UAF–GI) April 10, 2011 6 / 10

7. . . . permanent displacement . . .
Grapenthin et al. (UAF–GI) April 10, 2011 7 / 10

8. . . . and seismic waves (watch for those in the video)
Grapenthin et al. (UAF–GI) April 10, 2011 8 / 10

9. Preliminary observations from the animation
the actual slip of the Mw =9.0 earthquake is captured in frames
05:47:30-05:49:00
body waves (S-wave), causing small displacements, traverse the
array at about 8 km/s (this is apparent velocity, not S-wave
velocity)
surface wave, causing large displacements, travels at about 5
km/s
Grapenthin et al. (UAF–GI) April 10, 2011 9 / 10

10. Links
Preliminary Geodetic Slip Model of the 2011 M9.0 Tohoku-chiho
Taiheiyo-oki Earthquake (USGS):
http://earthquake.usgs.gov/earthquakes/world/japan/031111_M9.0prelim_geodetic_slip.php
Geohazards Supersite website – preliminary results:
http://supersites.earthobservations.org/sendai.php
Seismic wave propagation recorded on dense strong-motion
seismograph networks in Japan (K-NET/KiK-net):
http://outreach.eri.u-tokyo.ac.jp/eqvolc/201103_tohoku/eng/#knet
R. Grapenthin, Kinematic GPS solutions:
http://gps.alaska.edu/ronni/sendai2011.html
Grapenthin et al. (UAF–GI) April 10, 2011 10 / 10