Real Time Monitoring System for Megathrust Earthquakes and Tsunamis - Cabled Network System and Buoy System in Japan - 1
Subduction zones around the world Haiti Italy Turkey Tohoku Sichuan Taiwan Sumatra Chili New Zealand Huge earthquake (1999-2011) http://www.platetectonics.com 2
Model of Rupture Process at March 11 2011 EQ. From Associate Prof. Ide,University of Tokyo 3
Tsunami data observed by Pressure gauges Tsunami wave height Observed Tsunami data (ERI HP) Off Kamaishi cabled network data Initial water level TM2 TM1 TM1 TM2 Simulated Tsunami Off shore observation is very important 4
Nankai subduction zone Tokyo Osaka Nagoya Tonankai Tokai 2-3cm/y Hyuga-nada Nankai 5-6cm/y 4-5cm/y Philippine Sea Plate 5 M8+ class earthquakes occur every 100-200 years. 5
Historical events in the Nankai subduction zone 1707 CD(TONANKAI) + E(TOKAI) + AB(NANKAI) 1854 CD(TONANKAI) + E(TOKAI) 32hours AB(NANKAI) 1944 1946 CD(TONANKAI) 2years AB(NANKAI) M8 class EQs. are occurring with the interval of 100-200 years 6
Dense Oceanfloor Network system for Earthquakes and Tsunamis (DONET) 7
Landing Station Node Branching Unit 1900m Backbone Cable 4300m Ground Motion Sensing System Pressure Sensing System and Peripherals Extension Cable Remotely operated vehicle 8 8
Novel functions of DONET Redundancy: Equipping redundant configuration on backbone cable and node Osaka Tokyo Expandability: Branching unit and node enables wide-spread distribution of observation points. Number of Science Node : 5 Nodes Number of User Interface : 8 ports / Node Power Distribution : 30 W / Port Data Transmission : 50 Mbit / s / Port Precise Timing Control : < 1μsec Replaceability: Replacing observation unit at the seafloor by using underwater removable connector Maintainability: Operation on the seafloor by using Remotely Operated Vehicle (ROV) 9
Sensing systems Sensor Type specification Pressure sensing system seafloor Cable Ground motion sensing system Ground motion sensing system Gimbals Mechanism Finally buried Pressure sensing system (Nichiyu co. ltd) < < (Nichiyu co. ltd) < < 10
Installation of DONET system to the seafloor Japanese research ROV Hyper Dolphin Installed Termination Equipment 33-43.344N,136-33.209E,Depth:2009m Construction of Installation hole for seismometer Port Installation hole Installation of sensors 33-38.911N,136-36.210E Installed Science Node(A010) 33-43.349N,136-33.215E,Depth:2009m 11
DONET deployment movie 12
Current observation points Nodes (deployed) Observatories (deployed) Observatories (scheduled) Seventeen observatories are already working. More three observatories will be installed in this July to start full-scale operation. Construction of Installation hole for seismometer Installation of seismometer At March, 2011 ROV used in the submarine construction work: Hyper-dolphin Deployment of extension cable Installation of sensors 13
Data transfer system (DONET) DONET data will be open to the public Satellite systems are very important to support to data transfer systems 14
Seismic and tsunami data recorded by DONET 15
DONET records during the 2011.03.11 Tohoku great earthquake Time: 2011.03.11 14:56 (JST) Mw: 9.0 Depth 20 km 16
Records of the Tohoku eq. at DONET KMA02 station Strong-motion Seismograph Broad Band Seismograph Out of range 18 分 P wave KMA02 14:50:00(JST) 15:00:00 Quartz pressure gauge Differential pressure gauge Out of range Hydrophone Precision thermometer 17
All pressure gauge records of the Tohoku earthquake DONET successfully detected the tsunami wave of the M9.0 Tohoku earthquake in offshore. 19
Tsunami site amplification:comparison of offshore and near-shore tsunami waveforms from the Tohoku earthquake Near-shore tsunami height = Tsunami amplification factor Offshore height (DONET data) For improvement of real-time tsunami prediction Amplified by about 3 times Comparison of tsunami waveforms recorded by DONET-C9, Owase GPS tsunami meter, and Owase tide gauge from the 2011 Tohoku earthquake DONET-C09 detected the first tsunami wave of about 20 cm, about 20 minutes earlier than the costal tide gauge at Owase which recorded about 70cm tsunami height during the first wave.
Tsunami damage simulation From Dr. Sakaguchi JAMSTEC 21
DONET Phase 2 22
DONET Phase 2 (DONET2) A similar seafloor network system is needed for region off Kii Peninsula and Shikoku to decrease disasters caused by the subduction zone earthquakes in the Nankai Trough. We apply a high voltage system for DONET2 so that the observational area is twice of that of the current DONET. DONET1 Middle-voltage system (3KV) Cable length 300km + DONET type NODE 5 (40 oceanfloor sites) DONET2 High-voltage system (10KV) Cable length1000km + DONET type NODE over 10 (100 oceanfloor sites) 23 DONET2 DONET1 DONET2
Possible contribution on tsunami early warning 6min 6min 12min 12min The red parts show the DONET detects tsunamis earlier than land stations. 24
Expected slip on the plate interface after the Tonankai earthquake Fast (rupture) Afterslip of Tonankai earthquake propagates westward and triggers 25 nucleation of Nankai earthquake starts Slow (locked)
Expected seafloor deformation after the Tonankai earthquake Simulation of Nankai earthquake Afterslip of Tonankai earthquake Slip acceleration following afterslip Tonankai Tonankai Nankai Vertical displacement Nankai Vertical displacement Vertical displacement Tonankai 26 26 Days after Tonankai earthquake Days after Tonankai earthquake Days after Tonankai earthquake Nankai
Data assimilation Evaluate likelihood of the model successively comparing the simulation results and data from DONET with borehole measurements and GPS model model1 model 2 model 3 Vertical movement data now time Evaluate likelihood for large number of models comparing with data up to date model1 model2 The transition afterwards is predictable. model1 model2 likelihood 27 Sequentially obtained optimum value for parameters from waited average 27
DONET, DONET2, and DONET3 Tokyo Osaka Nagoya DONET DONET2 DONET3 Extended Part 28
Collaboration and Integration Further, we have to develop more network systems ESONET DONET: JAPAN MACHO: TAIWAN Asia: NEPTUNE CANADA/US Tokyo Taipei INDIAN OCEAN SOUTH AMERICA Map: Wikipedia The international collaboration is very important How to integrate the standardization and development 29
New Tsunami Buoy System
Development of new offshore buoy system for tsunami damage mitigation Real-time observation specialized for tsunami Mooring system resisting the strong ocean current (~ 5 kt.) Satellite communication Installation over densely-deployed area of the submarine cables Doubled iridium communication Tsunami measurement by single GPS observation at the sea surface Sampling rate of 30 seconds. 1000m-length wire with multiple cable cores Transducer below the wire Polypropylene rope φ19 Utilization of slack mooring Slack ratio: about 1.3 Releaser Nylon rope φ17 45 Bottom pressure data Tsunami height Potential observational region : Boso off Kanto 1677 Enpo earthquake (Mw 8.4) Anchor 3.7~4t Bottom unit(beam directivity ±45 ) Ocean-bottom pressure gauge (Watanabe, 1998)
Development of new offshore buoy system for tsunami damage mitigation Points 1. Quick installation to area earthquake risk highly speculated, such as Japan Trench, Western Nankai Trough, and Okinawa 2. Low cost and low installation work in comparison with cabled system 3. Enable deployment over densely-deployed area of the submarine cables 4. Satellite communication avoiding tsunami damage to coastal land station 5. High mobility
Further application to GPS-Acoustic observation for the seafloor crustal displacement RTK GPS Positioning Seafloor deformation observation is important to understand crustal stress accumulation leading the future subduction zone earthquake. GPS-Acoustic observation is good method, but not in real-time, not continuous data collection for the present system GPS base station Seafloor stations Acoustic Positioning Data transfer in real time Land station PPP GPS Positioning Schematic figure of the present GPS-Acoustic observation Seafloor stations Acoustic Positioning Schematic figure of the next-generation GPS-Acoustic observation Use of the buoy we suggested instead of the survey ship enable to the real-time, continuous observation of the seafloor deformation. 33
Concluding remarks :For improvement of earthquake and tsunami early warning Our marine technology contributes to mitigate earthquake and tsunami disaster in collaboration with satellite system Early detection and precise alert of seismic intensity and tsunami are helpful saving lives and decreasing damages DONET Offshore and near shore tsunami data New offshore tsunami buoy The 2011.3.11 Tohoku tsunami, the picture provided by Kyodo news Scheme of DONET data transfer in real time basis 34
Thank you for your attention 35