Kerry Sieh TO Annual Meeting 13 November 2007 Kerry Sieh TO Annual Meeting 13 November 2007 Soft corals lifted about 10 cm during the September 2007 earthquakes Behavior of the Sunda Megathrust in Sumatra

Caltech John Galetzka Mohamed Chlieh Don Helmberger JP Avouac Aron Meltzner Ozgun Konca Yaru Hsu Mark Simons Andrew Kositsky Indonesian Institute of Sciences Danny Natawidjaja Bambang Suwargadi Dudi Prayudi Imam Suprihanto Scripps Yehuda Bock Paul Jameson Peng Fang Linette Prawirodirjo Kyoto University Shigehiro Fujino USC Jose Borrero Soft corals lifted about 10 cm during the September 2007 earthquakes Collabora tors SponsorsSponsors

To understand the behavior of a great active fault at time scales important to understanding the earthquake cycle. Through the millennia Through the centuries During large earthquakes

base modified from NASA World Wind/Blue Marble from Rich Briggs, after Briggs et al 2006 Deformation over millennia

by Rich Briggs The earthquake cycle Nias-Simeulue section Mentawai section southern Aceh-Andaman section Deformation over centuries

Nias-Simeulue and southern Aceh- Andaman sections Fossil Microatoll deaths in 1861 Fossil Microatoll deaths in 1861 Fossil Microatoll deaths in 1843 Fossil Microatoll deaths in 1843 Fossil Microatoll deaths in ~1799 Fossil Microatoll deaths in ~1799 (tentative) Fossil Microatoll deaths in ~1440 Fossil Microatoll deaths in ~1440 Fossil Microatoll deaths in ~1390 Fossil Microatoll deaths in ~1390 Fossil Microatoll deaths in ~1327 Fossil Microatoll deaths in ~1327 from Aron Meltzner

The Mentawais

Bulasat Years (AD) Elevation relative to modern sea level AD 1357± & Sawtooth curve of paleoseismic events Not yet published

Simangan ya Years (AD) Elevation relative to modern sea level ±0.1 m 1.5±0.3 m 1.4±0.2 m 0.15 m ~0.2 m? Sawtooth curve of paleoseismic events Not yet published

Narrow trench-parallel graben on an islet west of South Pagai island

Victims of uplift -- dead Portuguese Men-o-War Southern tip of South Pagai island

from Briggs et al (2006) Vertical deformation in the field Mega island, 4˚S Measurements

Minor emergence near northern end of uplift Island at the western entrance to Sikakap strait

Field measurements

Map of field measurements Not yet published

Map of contoured field measurements Not yet published

Map of contoured field measurements Not yet published

Map of contoured field measurements Not yet published

L-band InSAR from the Japanese ALOR satellite

cGPS measurements Sumatran GPS Array (SuGAr) as of Sept 13, 2007 proposed early 2008

from Ozgun Konca

Horizontal (black) and vertical (red) Displacements during the M w 8.4 mainshock from Peng Fang via Ozgun Konca Map of cGPS displacements Not yet published

Silab u (SLB U) 15-sec cGPS from Jeff Genrich Strong-ground-motion from Chris Stephens via Ken Hudnut M w 8.4 K2 data Not yet publish ed 15-sec data Not yet published 1-sec data Not yet published

Comparison of K2 and cGPS velocity records at Silabu

Horizontal (black) and vertical (red) Displacements during the M w 7.9 aftershock from Peng Fang via Anthony Sladen Map of SuGAR vectors Not yet published

Silab u (SLB U) 15-sec 1-sec cGPS from Jeff Genrich Strong-ground-motion from Chris Stephens via Ken Hudnut M w 7.9 and 7.0 aftershocks cm 10 min 10 cm K2 data Not yet publish ed 15-sec data Not yet published 1-sec data Not yet published

Pukarayat (PKRT) cGPS from Jeff Genrich M w 7.9 and 7.0 aftershocks 15-sec sec data Not yet published 1-sec data Not yet published

Horizontal (black) and vertical (red) Displacements during the M w 7.0 aftershock from Peng Fang via Anthony Sladen Map of SuGAR vectors Not yet published

M w 8.4 inversions cGPS and teleseismic data by Ozgun Konca Teleseismic data only Data = black Model horizontal (red) and vertical (gray) Analyses Maps of inversions Not yet published

M w 8.4 inversions by Ozgun Konca Data = black Model horizontal (red) and vertical (gray) cGPS with coral at Mega Detail Map of inversions Not yet published

by Ozgun Konca M w 8.4 inversions Model displacements Horizon tal Vertical (m) from cGPS data only Maps of vertical deformation estimated from inversion of SuGAR data Not yet published

Joint seismic/cGPS inversion of the 7.9 aftershock by Anthony Sladen Data = black Model horizontal = red and vertical = gray Maps of inversion Not yet published

Joint seismic/cGPS inversion of the 7.9 aftershock by Anthony Sladen Maps of inversion Not yet published

Tsunami field data by Jose Borrero Measurements of runup along mainland coast Not yet published

Combined source of mainshock and two aftershocks -- M w 8.45 Data = black Model horizontal = red Model vertical = gray by Anthony Sladen Maps of slip from inversion Not yet published

from Jean-Philippe and Anthony Calculated interferogram from combined model

Base map from Mohamed Chlieh Comparison of 50-year coupling and September events How do the Sept 2007 events fit in to the long-term picture? Map Not yet published

from Mohamed, Anthony and Jean- Philippe

Accumulated potential slip versus slip during 8.4 in September Map comparing slip in 2007 with slip deficit since 1833 and 1797 Not yet published

Natawidjaja et al, JGR, 2006

Maps of 2007 uplift Not yet published

Bulasat Years (AD) Elevation relative to modern sea level 1797 & Sawtooth curve of paleoseismic events Not yet published

by Rich Briggs