1. Network Strain Filter and its applications on GPS data Matt Wei, Jeff McGuire WHOI September 10, 2011

2. Network Strain Filter Ohtani, McGuire, and Segall, 2010 Advantage: it doesn’t require the knowledge of deformation sources. GPS motion = secular motion + transients + site noise + reference frame error + seasonal motion + observation error Use Kalman filter for estimation. All variables are estimated simultaneously. Transients are expanded in spatial wavelets with time varying coefficients. Wavelets are good for expressing localized deformation.

3. 1. Southern Alaska Kodiak Island William Prince sound Kenai Pennisula Locked Postseismic reverse slip Creeping Zweck et al., 2002

4. Strain anomaly after 2010 - baseline plot for 3 stations relative to station AC59 on land

5. Transient field 2010-present 5 mm displacement within a year

6. 2. Salton Trough USGC

8. Example: Separating transients from 2000 Tokai Slow earthquake and dike intrusion, Nakai Trough, central Japan Miyazaki, et al., 2006 Horizontal Vertical Slow earthquake Dike intrusion

9. 3. The high-rate GPS data before the 2011 M9.0 Japan Earthquake Miyazaki, McGuire, and Segall, EPS, 2011 Horizontal transient field(foreshock – mainshock) GPS JPL 30 minutes solution minus reference frame error Benchmark + transient + coseismic Transient

10. M7.3 Foreshock (Mar. 9) Slip Distribution Aseismic Slip between the foreshock (Mar. 9) and mainshock (Mar. 11) The mainshock's epicenter may have been triggered by afterslip that followed the foreshock. Miyazaki, McGuire, and Segall, EPS, 2011 Foreshock Mainshock (JMA) Mainshock (USGS)

11. Summary Network Strain Filter method – model transients as spatial wavelets and does not require the knowledge of deformation sources. Southern Alaska: strain anomaly between Kenai Peninsular and Kodiak Island after 2010 Salton Trough: postseismic deformation of El Mayor Earthquake and possible slip transients before the earthquake Northeast Japan: afterslip of foreshock might have triggered the mainshock.

12. Automate detection of fault creep in InSAR data (poster A-065) 11/27/2009 - 4/16/2010 Mean = 0.02

13. Thanks

14. Seasonal motion

15. Postseismic displacement for 1 year after the mainshock (max about 8 cm) 1 cm