GNSS (GPS) buoy array in the Pacific for natural disaster mitigation. Teruyuki KATO Earthquake Research Institute the University of Tokyo, Japan

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1 GNSS (GPS) buoy array in the Pacific for natural disaster mitigation Teruyuki KATO Earthquake Research Institute the University of Tokyo, Japan 1

2 (Modified from Oki & Koketsu, 2011) Historical megaquakes occur only along the subducting plate boundaries. And these earthquakes generate large tsunamis 1952 Kamchatka EQ(Mw9.0) 1957 Andreanov EQ(Mw9.1) 2011 Off Tohoku EQ(Mw9.0) 1964 Alaska EQ(Mw9.2) 2004 Sumatra EQ(Mw9.0) 2010 Central Chile EQ(Mw8.8) 1960 Chile EQ(Mw9.5)

3 Tsunami early warning for distant earthquake is provided through Pacific Tsunami Warning Center, Hawaii 3

4 Plate boundary in the south Pacific Plate velocities are shown in mm/yr (Figure taken from web by Y. Ishikawa) 4

5 65 M>7.0 earthquakes in the south Pacific region ( ) USGS 5

6 Recent significant tsunami earthquakes in the south Pacific region Solomon Islands M7.6 (13 Apr. 2014) & M7.5(19 Apr. 2014) Solomon Islands M8.0 (6 Feb. 2013) Vanuatu M7.8 & Santa Cruz Is. M7.7(7 Oct., 2009) Samoa Islands Mw8.0 (29 Sep. 2009) Solomon Islands Mw8.1 (1 Apr. 2007) 6

7 Countermeasures for natural disaster is a key for SDG in the countries in this region Earthquake and tsunami is one sample among other natural disasters. Monitoring environmental parameters are fundamental for natural disaster mitigation Temperature, pressure, rainfall, wind : typhoon etc. Seismic waves, crustal deformations: earthquake Sea-surface variations: sea-level rise, tsunamis Total electron content: ionospheric disturbance These observations have been done mostly at on shore sites but data should be taken off shore as well for better early warning against natural disaster GNSS buoy is a solution for this problem, in particular in the ocean 7

8 Tsunami (sea-surface) sensors Tide gauge Super sonic sensors Pressure sensors Satellite altimetry GPS buoy

9 Basic concept of sea-surface monitoring using GNSS (GPS) buoy GPS Satellite Base Station GPS Tsunami Meter Data RTK-GPS in baseline mode was implemented Distance limit: less than 20km 9

10 GPS buoy for operational test off Ofunato, northeastern Japan 2003Tokachi Data were transmitted to the City Hall and Fire station 1.6km φ:2.8m H:8.2m Weight:12ton Water depth:50m 10

11 Peru Earthquake JST25/06/2001 Original 1Hz sampled data 11

12 Peru Earthquake JST25/06/2001 Filtered buoy data and tide gauge data Tsunami GPS Buoy Tide Gauge 25 June 2001 (JST) 12

13 GPS buoys implemented as wave meter operated as a national wave monitor system NOWPHAS (From ERI HP) System uses RTK-GPS and data transmission by radio. Placed within 20km from the coast. Established at 15 sites as of Real time monitor on the Web is available. 13

14 Observed tsunamis due to the Tohoku-Oki earthquake on 11th March 2011 by GPS buoys EQ:14h46m Off North Iwate (Kuji) Off Central Iwate (miyako) Off South Iwate (Kamaishi) 15:18 First very large tsunami arrived at Iwate 15:14 Tsunami alert was updated to higher than 10m at Miyagi & 6m at Iwate 15:10 Acute sea-level rise was observed at JMA 14:50 First tsunami alert by Japan Met. Agency (Miyagi 6m; Iwate 3m) 14 (Courtesy of Port and Airport Research Institute)

15 Lessons from the 11 March Tohoku-oki tsunami and their countermeasures GPS buoy should be placed much farther offshore for effective early warning (>100km) Problems to be solved for far-offshore buoy deployments 1. Baseline mode kinematic observation has distance limit for accurate measurements (<20km). New algorithm of Precise Point Positioning should be introduced 2. Surface radio system is not adequate for long distance data transmission Data transmission via satellite is needed 15

16 New algorithm: PPP-AR (Precise Point Positioning with Ambiguity Resolution) GPS satellite IGS (International GNSS Service) Precise orbit (sat. orbit and clock) + correction by GEONET) GPS receiver Control station 1Hz data GEONET Conventional PPP uses only IGS orbits/clock. New PPP-AR uses corrections by GEONET data 16 T15,O48

17 Experiments with QZSS & ETS-VIII (Michibiki) (Kiku 8) Period of experiments 16 Dec Jan., Jun., 2014 Purpose - Correction data transmission using LEX/QZSS - Positioning data transmission via ETS-VIII. - Real-time data dissemination through internet 17

18 Experiments with QZSS & ETS-VIII 18

19 Multi-purpose GNSS buoy for disaster mitigation More effective tsunami early warning at far offshore Ocean bottom crustal movements Continuous monitoring by GPS/Acoustic system Atmospheric research (GPS meteorology) Contribution to weather forecast Ionospheric research Contribution to space weather forecast Ocean surface monitoring with ancillary equips High speed satellite communication is required 19

20 Ocean bottom crustal movement observation using GPS/Acoustic system GPS satellites Kinematic GPS GPS base station Acoustic ranging Survey vessel Ocean bottom stations Slides provided by Mariko Sato (Japan Coast Guard) 20

21 Velocity of ocean bottom stations before the 3.11 Eq. Velocity by GPS-acoustic system Velocity by GEONET (Japan Coast Guard, File submitted to the Earthquake Research Committee)

22 Application to ocean bottom crustal movements monitoring using GNSS buoy GNSS sat. Comm. Sat. Internet GPS buoy Receiving sonic wave Receiving site Kochi Users N. C. Sending sonic wave Ocean bottom station (3 sets) 22

23 Experiment in 2013 Deployments of ocean bottom stations 29 July 2013 CTD observation: 31 July 2013 PS/Acoustic ranging using buoy: August 2 October, 2013 GPS/acoustic ranging using a boat: 31 July

24 Application of GNSS buoy for weather forecast (Meteorological Research Institute, Japan) GPS buoy and GEONET sites Time series of ZTD between GEONET(1121) and buoy Comparison is made between buoy and the GEONET site of the lowest height nearby the buoy. Data period: 1-16 August 2008 Time series at the buoy ( ) is generally consistent with that on the ground ( ), yet the former differs from the latter at some time periods. More satellite number provides better agreement between the two, implying adding satellites other than GPS, such as GLONASS, may improve the results. 10 satellites 6 satellites 24 (Y. Shoji:Spring Meeting of MSJ 2010)

25 TEC variation observed at the 2011 Tohoku earthquake by NICT TEC variation observed using GEONET data. Short period variations with less than 10 minutes of periods are shown. X indicates ionospheric epicenter. Concentric circle is centered at the ionospheric epicenter. Cut-off elevation angle is 15deg. (translated from the slide by Tsugawa, NICT) 25

26 Global ground-based GNSS network - Next step to the oceanic region (National Institute of Information and Communications Technology, NICT, Japan) More than 5,000 ground-based GNSS sites data are available online as of Jan. 2012, over the world. More distributed GNSS sites in the ocean, together with more GNSS satellites, improves spatial resolution and decreases blank area. (translated from the slide by Tsugawa, NICT) 26

27 Proposed GNSS buoy array in the western Pacific Expected cost for 81 sites: (Very coarse!) Construction 300million$ Operation 10million$/yr Feasible? or Not? (81 sites in the Japanese EEZ; Modified from Tsugawa et al., 2012) 27

28 Outlook for sustainable development in the Pacific countries by GNSS buoy array Society resilient against natural disaster is a key for development of a country GNSS buoy array around island country is a powerful tool for making a strong country against natural disaster, as well as monitoring sea level rise due to global warming. Japan has a technology of GNSS buoy for natural disaster reduction for contributing to Pacific island countries Further, GNSS buoy array can be a fundamental social infrastructure for monitoring earth; ocean bottom crustal deformation, ocean surface, atmosphere, ionosphere., which is important for maritime industry, fishery, maritime traffic, etc., which will make coastal people more intelligent on the nature and more happy. 28

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