Presentation on theme: "1 GRACE Observations Challenging the Long- Held Tsunami Theory Tony Song, January 2007 Y. Tony Song (JPL) & Shin-chan Han (GSFC) Related publications Song."— Presentation transcript:
1 GRACE Observations Challenging the Long- Held Tsunami Theory Tony Song, January 2007 Y. Tony Song (JPL) & Shin-chan Han (GSFC) Related publications Song et al., The 26 December 2004 tsunami source estimated from satellite radar altimetry and seismic waves, GRL, 32, doi:10.1029/2005GL023683 (2005). Song et al., Did the horizontal impulses of the continental slope dictate the 26 December tsunami genesis?, OM, revised. (2006). Song, Detecting tsunami formation and scales directly from GPS displacement measurements, GRL, 34, doi:10.1029/2007GL031681 (2007).
2 Tony Song, January 2007 Tanioka & Satake (1996): “ We ignore the horizontal motion of water due to movement of slope, because …(Iwasaki).” Long-held Tsunami Theory “Seafloor uplift is the main cause of tsunamis” Pond & Pichard (1983): “ Earthquakes that involve a significant vertical motion are more effective in generating tsunamis than those that primarily horizontal motion.” Long-wave theory: Webb (1962) Kajiura (1963) Hwang & Divoky (1970) Textbook
3 Tsunami Models based on the “Theory” (Steve Ward) Science (2005) Titov et al. Science (2005)
4 Compare the “Theory” with Data Titov et al. Science (2005) GPS data from Vigny et al. (2005); Subarya et al. (2006)
5 To verify the theory? It is difficult from In-Situ Measurements Meltzner et al, JGR (2006) Data: 0.6~1.5 m Moran et al, EOS (2005): “Only a small area of seafloor uplift was found” Survey: Too Small?
6 Grace Seafloor uplift TOPEX/Poseidon Sea Surface Height Ocean Launched 2002 TOPEX, Jason and Envisat measure SSH changes. GRACE measures gravity changes. Measurements from these two satellites have to be consistent.
7 Seismic and GPS data Tony Song, January 2007 Green arrows from seismic data Blue arrows from GPS displacements (red arrows) data
8 Method: Combine Seismic and GPS Data Seismic and GPS models (2004 Sumatra): M1 – seismic inversion M2 – continuous GPS inversion M3 – long-term seismic and GPS microGalileo=10^-8m/s2 Earthquake deformation Corresponding gravity changes
9 GRACE-observed gravity changes (microGalileo=10^-8m/s2) GRACE decomposed: Surface change Crustal density change Reference: Han et al. Science, 2006 Chen et al. GRL, 2007 A. SurfaceB. Sub-surfaceC. (A + B)D. GRACEModel-GRACE uplift 9.864.226.196.020.03 subsidence-5.02-13.97-11.10-10.860.02
10 Compare with Satellite (2004 Tsunami) Tony Song, January 2007 The vertical uplift displacement alone is not enough to have generated the 2004 tsunami. Ocean dynamics
11 Summary 1 Tony Song, January 2007 GRACE observation is consistent with seismic and GPS inversions. However, the vertical uplift displacement alone is not enough to have generated the powerful 2004 tsunami observed by altimeters (TOPEX, Jason, Envisat). Next: What is the main force of tsunamis?
12 Tony Song, January 2007 Continental Collision into the Ocean Total tsunami energy: E T = PE + KE Horizontal (Song et al 2006) Vertical (Tanioka & Satake 1996)
13 Horizontal + Vertical (2004 Tsunami) Tony Song, January 2007 Based on the new theory, both seismic and GPS data can predict the tsunami height.
14 GPS prediction of tsunamis based on the new theory (Song, GRL, 2007) Tony Song, January 2007 Earthquake Model OGCM Tsunami Model
15 Summary 2 Tony Song, January 2006 For decades, people have believed that the seafloor uplift is the only cause of tsunamis. We have found: 1. The seafloor uplift is not enough to have generated the 2004 tsunami. 2. The horizontal slip of continental slopes is likely the real cause. Lat two years: March 2005 Nias M8.7, false alarm June 2005 North California M7.1, false alarm May 2006 Tonga M7.8, false alarm July 2006 South Java M7.7, no alarm; but 600 people were killed. November 2006 Kuril Islands M8.3, false alarm January 2007 Kuril Islands M8.1, false alarm February 2007 Solomon Islands M8.0, 30 killed
16 At United Nations Description of Event: JPL’s tsunami prediction concept was selected and reported at UN’s EWC3, Mach 25~30, 2006, Bonn, Germany German newspaper report: “Tension at the border” …Tony Song of NASA broke silence on Tuesday at the international early warning conference in Bonn. Before the event, former US president Bill Clinton and Federal Minister of Foreign Affairs Frank-Walter stone Meier and more than 1000 scientists urged to furnish as fast as possible warning systems for Tsunamis. But now Song demonstrated his colleague that they had not understood the cause of the giant waves correctly. According to the established theory a Tsunami develops, if the sea water gets an impact with a sea-quake transferred by the sea- bottom: The soil moves thereby like a piston perpendicularly upward, it is said. Song meanwhile found out that the Tsunamis was released on 26 December 2004 particularly when lateral breaking the soil….