Advanced ocean floor observatory for mega-thrust earthquakes and

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					Advanced ocean floor observatory for
      mega-thrust earthquakes
   and tsunamis around the Nankai
     Trough, Southwestern Japan



                            Yoshiyuki KANEDA
                                DONET GROUP
      Department of Oceanfloor Network System Development for Earthquakes and Tsunamis
                                        DONET
                    Japan Agency for Marine-Earth Science ant Technology
                                       JAMSTEC
Previous research in the Nankai trough

                                       Historical EQs. in the Nankai trough

                                         year    age     A B C
                                         1605   KEICHO            ?

                                         1707   HOUEI


                                         1854   ANSEI


                       KII peninsula     1944   SYOWA

       NANKAI TROUGH
                                         1946   SYOWA
                  PSP

                                         A;Nankai EQ.
                                         B;Tonankai EQ.
                                         C;Tokai EQ.
he results of mega-thrust EQ. recurrence
 cycle simulation in the Nankai trough
 ① Tonankai+Nankai                            ② Tonankai+Tokai            Nankai



                                                                 7days
                                  111 years




     Nankai    Tonankai   Tokai
                                                                                103years
 ①
        111 years
                                              ③    Nankai                 Tonankai
 ②            7days


        103 years                                                97days


 ③             97days
Advanced Ocean Floor Cable System



                         Image




Outline & Concept
Ocean floor cable network system
as MEXT project




                               Sensors
                          ・ over20 Seismometers
                          ・ 20 Pressure gauges
海底ネットワークシステムコンセプト
   Outline of ocean floor cable system
                     Landing Station

                     Backbone cable system

                      Brunch unit

                     Sensor system
                     Seismometers,
                     Pressure gauge



                  High Reliability Backbone Cable System
                   Replaceable Observatory Node
                   Extendable Advanced Sensor System
Data Application
・Speedy evaluation and notification for earthquakes and tsunamis.

・Provide observed data such as ocean floor deformation derived from pressure
 gauges to improve the simulation and modeling researches about the mega-
 thrust earthquakes. (Data assimilation)
・Understanding of the interaction between the crust and upper mantle around
 subduction zone.
Maintenance systems of JAMSTEC
 3000m Class ROV          7000m class deep sea ROV
 「HYPER-DOLPHIN」               「KAIKO7000」




      Deep Sea Cruising AUV 「URASHIMA」
Advanced Ocean Floor Cable System



   Network Array Planning
           Network array planning


               Kii Peninsula
                               Tonankai Seisomogenic Zone




Nankai Seisomogenic Zone


                                                      sensor
                                                      node
                                                      Back bone
                                                      cable
Advanced Ocean Floor Cable System



                         Image
  海域でおこる地震活動の検知
  The resolution test of hypocenter
determination using oceanfloor network




                      Network Array Good resolution!!
  The checker board test for offshore
         geodetic data analyses
                         Model                              Land GPS



40km square
checker board
Slip rate : ±1m




   Ocean network system(36 pressure gauges)+ Land GPS

                                               ▲:Land GPS and Pressure gauge
                                               Resolution
                                                ・Land GPS:
                                                        horizontal; 1mm
                                                        vertical; 3mm
Good resolution!!                                ・Pressure gauges: 10mm
Around network array
Advanced Ocean Floor Cable System
             Sensors
   1)Multi seismometers for
               ・Broad band phenomena
               ・Strong Motion
               ・Micro EQs.
   2)Precise pressure gauges for
               ・Tsunami
               ・Ocean floor deformation
   3)Data storage function at the trouble

           Under development
   *Precise ocean floor deformation
    monitoring system
   *Advanced in lined sensor cable
    system
Research on real time estimation
of source elements using network
data (regional analysis)
                                                                          ①
                                                                         Observe seismic
                                                                         wave by network
                                   ②
                                   Gather data

                                                                               Database
                    Tonankai Eq.
   K-net                                                                      Synthetic
                                                                              waveform

                                                                         Analyze with
                                                                     ③
                                                                         theoretical data
                                                                                  Structure model
           Ocean floor network
                                                          ・Magnitude              by JAMSTEC
                                         ③   Analyze
                                                          ・Focal mechanism
                                                          ・Asperity area



                                         ⑤                    ④

             Construct source model and           Provide the estimated results before
             pre-estimate Tsunami waveform        arriving seismic wave in populated area
  Improve simulation model
Improve the simulation model

Data assimilation:
using pressure gauge data as
ocean floor deformation monitoring

Keyword: Long term observatory
                     Data assimilation
Observation data
                               Predict 2
                                     Predict (n)



           Optimization         Long-term predict
                                using predict (n)
                                                    time
  Time range for data assimilation

                   Improvement Simulation model
                                                       Without improvement



                            Improvement
                                                                       time
           Network data flow
Network




 Land        JAMSTEC           analyses
 Station     Data center


                            JMA       analyses
                           Others
Advanced Ocean Floor Cable System




                         Image
Ocean floor cable network system
as MEXT project




                                Sensors
                           ・ over20 Seismometers
                           ・ 20 Pressure gauges


                            Project
                            ・ FY2006-FY2009
                               4 years
System Concept
・Redundancy, Extension and advanced maintenance system
using the looped cable system, junction boxes and the ROV/AUV etc.

    Keywords: Landing both cable end, Node, Brunch unit




Data Application
・Speedy evaluation and notification for earthquakes and tsunamis.

・Provide observed data such as ocean floor deformation derived from pressure
gauges to improve the simulation and modeling researches about the mega-
thrust earthquakes.
・Understanding of the interaction between the crust and upper mantle around
subduction zone.
           Future
           Plan??



                           Nicoya



                                    Osa




Ocean floor cable network system