Yutaka HAYASHI 1, 2. Graduate student, Graduate School of Engineering, Tohoku University

Transcription

1 3 July, 2008 September at Meteorological 11-12, 2008 Research in Pavia, Institute Italy 6th International Workshop on Remote Sensing for Disaster Management Applications Yutaka HAYASHI 1, 2 1 Graduate student, Graduate School of Engineering, Tohoku University 2 Senior Researcher, Seismology and Volcanology Research Department, Meteorological Research Institute, Japan Meteorological Agency (MRI, JMA)

2 1. Introduction, Backgrounds Satellite altimetry 2004 Sumatra-Andaman Earthquake Importance of tsunami observation data in an open sea 2. Extraction of 2004 Indian Ocean tsunami signals from satellite altimetry data Methods: Multisatellite interpolation Results: Tsunami profiles along 5 satellite tracks 3. Tsunami detectability of the altimetry mission Meaning of the residual error To do in near future 4. Summary Index

3 1. Introduction, Backgrounds Satellite altimetry 2004 Sumatra-Andaman Earthquake Importance of tsunami observation data in an open sea 2. Extraction of 2004 Indian Ocean tsunami signals from satellite altimetry data Methods: Multisatellite interpolation Results: Tsunami profiles along 5 satellite tracks 3. Tsunami detectability of the altimetry mission Meaning of the residual error To do in near future 4. Summary 1-index

4 Altimeter Microwave sensor (C- and K-band) Accuracy of observation Jason-1 <4.2cm TOPEX/Poseidon 4.2cm (RMS),... Sampling approx. every 5-10km Missions Ocean monitoring, etc. List of altimeter-equipped satellites satellite operation, data processing cycle (day) 2006 Jason-1 TOPEX/Poseidon CNES, NASA Jason GFO NOAA ENVISAT ESA, CNES A-1

5 Raw data involve noises caused by Ocean tides Air pressure Offsets of each satellite Geoid locality, etc. reduced by routine processing by operating agencies SLA (sea level anomaly) Nonseismic effects Sea currents Temperature Winds etc. (freely distributed products) Near Real-time 1 2 days oceanographers interest Delayed time 3 6 months 1-A-2

6 Observations of sea level change IPCC WG1 (2007) reported Current rate of sea level rise 1993 to 2003 : 3.1 ± 0.7 mm / yr (by altimetry) Sea level change in observed by satellite altimeters 1-A-3

7 Map of monthly mean sea level anomaly cm 1-A-4 (From website of Japan Meteorological Agency)

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9 B-1 Location Chile Prince William Sound, Alaska Off the West Coast of Northern Sumatra Kamchatka Off the Coast of Ecuador Rat Islands, Alaska Northern Sumatra, Indonesia Andreanof Islands, Alaska Assam - Tibet Kuril Islands Banda Sea, Indonesia Kamchatka Date UTC M by USGS(2006)

10 Observed outside of the Indian Ocean by tide gauges Indian Ocean offshore tsunami height (by model) : 10cm order in the Indian Ocean 24 h epicenter 24 h 24 h 18 h 18 h 6 h 18 h Model Offshore Amplitude 12 h 12 h 1-B-2 After Titov et al. (2005)

11 Rough Estimation of tsunami height O.T min. O.T min. 1-B-3 Hirata et al.(2006)

12 Important information. Why? Rich in the information near the trench Less affected by nonlinear effects Application (example) Slip distributions by linear inversion of tsunami waveforms Tsunami source generated slowly (<1km/sec)? (by Hirata et. al, 2006) 1-C-1 Hirata et. al (2006, EPS)

13 Raw data involve noises caused by Ocean tides Air pressure Offsets of each satellite Geoid locality, etc. SLA Nonseismic effects Sea currents Temperature Winds etc. Tsunami Coseismic geoid change (products) oceanographers interest Seismologists interest reduced by routine processing by AVISO vanishingly small (by Hayashi et al., 2007, EPS) separate 1-C-2 An improved tsunami profile has the potential to contribute towards a more accurate analysis of the Indian Ocean tsunami

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15 Horizontal plane can be deformed Why 1. fault slip 2. mass redistribution 3. disturbance of gravity field 4. change of geoid (almost equal to the average sea surface height) Illustrated by Fumi Hayashi 1-C-3 Hayashi et. al (2007, EPS)

16 Fault Hayashi et. al (2007, EPS) 1-C-4

17 1. Introduction, Backgrounds Satellite altimetry 2004 Sumatra-Andaman Earthquake Importance of tsunami observation data in an open sea 2. Extraction of 2004 Indian Ocean tsunami signals from satellite altimetry data Methods: Multisatellite interpolation Results: Tsunami profiles along 5 satellite tracks For more details, please refer Hayashi(2008,JGR). 3. Tsunami detectability of the altimetry mission Meaning of the residual error To do in near future 2-index 4. Summary

18 Jason-1 ENVISAT TOPEX/Poseidon Jason-1 (approx. 115 min after the main shock) TOPEX/Poseidon (approx. 120 min) ENVISAT (approx. 190 min) Mainshock, and aftershocks within 12h Within 12h from the main shock 2-A-1

19 Data Altimetry data from four satellites Sampled data near from reference points Data not affected by tsunami are used R=45 3km day < T< +10 3day All tracks from four altimeter equipped satellites 2-A-2

20 SLA ref (,,t) = w i SLA obs,i / w i (Eq. 1) w i = exp (-r i 2 / R 2 - t i 2 / T 2 ) (Eq. 2) r i : the distance between the location of ith datum and the tsunami searching point (,,t) t i : the time difference of observations between a tsunami observation point (t) and the ith datum R, T: scale parameters h tsunami (,,t) = SLA obs (,,t) -SLA ref (,,t) (Eq. 3) SLA obs : an anomaly in an observed sea surface height SLA ref : the reference height defined by Eq. 1, 2. Eq. 3 is applied to the sampling points of the tsunami field (Section 2.3(1)). Example of weight for the point maximum tsunami height is detected along Jason-1's track109 An area of circle is propotional to w i 2-A-3

21 Relation between scale parameters and RMSEs Typical scale of mesoscale eddy in this region 45km, 10days (Stammer,1997) 2-A-4 Hayashi (2008, JGR)

22 Simpler wave form Smaller heights Peak 0.7 m -> 0.6 m Defined at more sampling points This Study SSH c#109 SSH ref Conventional method SSH ref cycle#109 O.T min. cycle#108 cycle#109 SSH c#109 SSH c#108 O.T min. 2-B-1 Hayashi (2008, JGR)

23 min from mainshock min 2-B min min Hayashi (2008, JGR) detected wave front

24 Hayashi (2008, JGR) 2-B-3

25 RMSE halved small number of lack-of-data Please compare: RMSE of SSH by Jason-1 is approx. 4cm. Hayashi (2008, JGR) 2-B-4

26 1. Introduction, Backgrounds Satellite altimetry 2004 Sumatra-Andaman Earthquake Importance of tsunami observation data in an open sea 2. Extraction of 2004 Indian Ocean tsunami signals from satellite altimetry data Methods: Multisatellite interpolation Results: Tsunami profiles along 5 satellite tracks 3. Tsunami detectability of the altimetry mission Meaning of the residual error To do in near future 4. Summary 3-index

27 RMSE(4-5cm) by this method reference heights are defined by using future data (+30days) may related to the limit of delayed time analysis REMS(7-10cm) by conventional method reference height can be obtained beforehand may related to the limit of near real-time analysis This method Any other methods? past ±30days Conventional method future 1 cycle 3-A-1 Observation date used to define reference height, and date of tsunami

28 "Urgent need to consider a more closely integrated approach, which would defined and evaluate the strengths and weaknesses of each element - buoys, models, satellites -, of a combined detection system. " ( from "Report on Tsunami Workshop during Pan Ocean Remote SEnsing Conference symposium in Nov in Busan) 3-B-1 GPS buoys (by ERI, Tokyo Univ. and others) Ocean bottom sensor system (JAMSTEC, and others)

29 Team core members : Y. Hayashi, K. Hirata, M. Kamachi (MRI) advisors : S. Koshimura (Tohoku Univ.), M. Okada (MRI OB) To do until 2011 Searching past SLA data to find tsunami signals from other events. Estimating tsunami detectability by no-going or future possible altimetry missions; evaluate feasibility for (near) real time tsunami monitoring in the future. etc. GANDER (Allan,2006) Wide-swath altimeters 3-B-2 Example of future possible missions

30 The multi-satellite time-spatial interpolation method effectively reduced the oceanographical backgrounds in the SLA data Then, less-noisy tsunami data of the Indian Ocean tsunami from satellites are successfully obtained These datasets should have potential to contribute more accurate analysis of Indian Ocean tsunami. Ongoing altimetry missions may have potential to find tsunami higher than 10cm (delayed time analysis) or 20cm (near real-time) in the open ocean. 4-1

31 The satellite altimetry data and processing codes were provided by AVISO, CNES (Archivage, Validation et Interprétation des données des Satellites Océanographiques, Centre National d Etudes Spatiales) Some of the figures were prepared by using General mapping tools developed by Wessel and Smith (1999) Some of the figures were illustrated by F. Hayashi. This study and travel expense are partly supported by Grant-in-Aid for Scientific Research (KAKENHI no , ) by JSPS and MEXT. 4-2

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