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Unveiling Sumatran Subduction: From Paleoseismology to Neotectonics

Investigating fault behaviors across time scales. Addressing challenges of plate boundary roles and knowledge dissemination.

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Unveiling Sumatran Subduction: From Paleoseismology to Neotectonics

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  1. TO Sumatran Subductionproject Investigations across many time and length scales Paleoseismology, rupture processes Hundreds to thousands of years Neotectonics, orogeny Tens of thousands to millions of years

  2. Three challenges: • How do faults behave through many earthquake cycles? Why? • What roles do the various components of an obliquely convergent plate boundary play? • How can we transmit our discoveries to those who would benefit?

  3. How do faults behave through many earthquake cycles? And why? • Let’s start with the historical period

  4. In this area, corals show that the only large event in 200 years has been the M 7.7 rupture of 1935

  5. Modelling of the coral sealevel records show a large component of aseismic slip on the subduction interface here

  6. Corals farther south reveal a history of giant ruptures of the subduction interface

  7. Modelling shows two recent giant events have involved rupture of the same patches 1797, M > 8.4 1833, M > 8.7

  8. How do faults behave through many earthquake cycles? • Now let’s look farther into the past

  9. Some sites within this patch show several closely spaced couplets within the past millennium ~960 AD 1600 AD ~1000 AD 30 cm 1650 AD 1797, M > 8.4

  10. At a few sites the coral record shows nearly periodic repetition of uplift events 1797, M > 8.4

  11. At a few sites the coral record shows nearly periodic repetition of uplift events 1797, M > 8.4

  12. Suggest that the depth of locking of the subduction interface varies along strike Submergence rates of the past 50 years

  13. The locking depth appears to correlate with the size of past earthquakes Submergence rates of the past 50 years 1935 1797 + 1833

  14. Mapping the great 2002 rupture inspired many questions Modeling of campaign and continuous GPS velocity vectors also suggests that the depth of locking varies widely along strike

  15. Mapping the great 2002 rupture inspired many questions To improve our measurements of deformation, we began installing the Sumatran GPS Array (SuGAr) in 2002

  16. Telemetry antenna Solar panels Micro-Z receiver Satellite terminal Antenna A typical SuGAr station

  17. How can we transmit our discoveries to those who would benefit?

  18. In 2005, we’d like to pursue these activities: • Continue modeling of coral and GPS data • Install 16 more GPS stations • Install 2 strong-ground motion instruments over the locked patches • Begin investigations of historical and instrumental seismicity • Restart efforts to determine the rate of slip on the Sumatran fault • Continue our educational outreach efforts

  19. In future years, we hope to add other components: • Bathymetric data for tsunami modeling and structural interpretations • Additional coral data to constrain events, rates and tsunamis • Passive seismic transect to map subduction interface • Heat-flow measurements to constrain thermal profiles

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