Japan earthquake disaster assessment using RS tech

Japan earthquake disaster assessment using RS tech

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Kazuo Yoshikawa, Susumu Takagishi and Yuki Okajima
PASCO Corporation, Japan
Email: [email protected]

Introduction
A massive earthquake of 9.0 magnitude hit off the coast of Tohoku, Japan, on March 11, 2010. It caused devastating damages over wide areas of the East Japan, particularly along with the coastline of the Pacific Ocean. PASCO contributed to the disaster monitoring for mitigating by using remote-sensing (RS) technology and varieties of image data from satellites, helicopters, vehicles and ships.

TerraSAR-X captured a series of images during March 13 to April 4, over the affected tsunami areas. Automatic extraction of inundation areas from the satellite images was effective. Oblique images from PASO’s sensor were also collected to observe the specific areas of the severely damaged regions. Mobile mapping systems were also used to comprehend the conditions of damaged sites. This paper presents an example of disaster monitoring and mitigation activities.

Concept for the monitoring
Concept for the disaster monitoring and mitigation is as follows:

  • Observing wide area information and creating three dimension data.
  • Speedy day and night observation.
  • Narrow area with higher accuracy.
  • Quick analysis of acquired data from various sensors, its visualisation and supply.
  • Data relay and immediate processing in the areas of disaster.


Fig.1 Concept for disaster monitoring
Fig.1 shows PASCO’s concept for disaster monitoring. PASCO in approximately 4 years, after the launch of TerraSAR-X (TSX), has successfully carried out about 30 studies of disaster response worldwide. Through these studies, the company aims to develop integrated social system and providing information within three hours. To realise this concept, global disaster monitoring has been put into practice since 2008 (PASCO, 2011).

Action for the East Japan earthquake

1) Data acquisition using a variety of platforms and sensors
One of the characteristics of damage caused by this earthquake is due to its wide area. Immediately after the disaster, researchers gathered wide area information using satellites and airborne tools (Fig.2).


Fig.2 First actions within 72 hours
TerraSAR-X is one of the most suitable option as an emergency mean to grasp the disaster situation since its SAR sensor is independent of weather conditions and daylight. TerraSAR-X is also useful for monitoring activity, considering its revisit cycle is 11 days. Airborne photogrammetric digital camera images were acquired over severely affected and important areas such as harbours and cities and coast lines. High resolution panoramic aerial images from helicopter covered the areas, where damage was serious, for reconstruction plans. All of optical sensors depend on weather and it is best-effort basis.

Mobile mapping system (MMS) was utilised in affected areas for road management. The system consists of laser scanners and digital video scanners

2) First actions (within 72hours)
At 14:46pm on March 11 (JST), people were evacuated temporarily due to strong shaking in Tokyo, despite the fact that they were more than 500km away from the epicentre. After a temporary confusion subsided, researchers started planning for the disaster monitoring. Fig.2 shows our first action within 72 hours.

The day of the earthquake, we created distribution maps of seismic intensity, lowland and range effects from Fukushima nuclear power plant.

On March 13(48hours), the topographic change map was created after tsunami around the Sendai city utilising superimposed TerraSAR-X images acquired on October 21, 2010 (before the disaster) and March 13, 2011 (after the disaster). This map indicates the change of the ground surface roughness utilising the characteristic of TerraSAR-X images.

The yellow area of the map is estimated flooded areas using photogrammetric method. The analysed data was showing that the tsunami reached approximately 6 km inland. On March14 (72hours), detection of floating objects were shown.


3) Maps of flooded areas for 500 km coastline (Within 1st week)
The estimated flooded areas along the East Japan coast were visually interpreted from pre and post-disaster satellite images with topographic maps (PFM*)overplayed. Target area was 500 kilometres long from Aomori Pref. to Ibaraki Pref. A total of 50 technical experts went into this project from March 12 to March 18(Fig.3).

Images from AVNIR-2(ALOS), RapidEye, WorldView-1,2, SPOT and Aerial photo were contributed and useful. The 2.5m pan-sharpened colour image from ALOS (PSO**)acquired before the earthquake was utilised as reference. On March 23, the maps were updated with finer photogrammetric orthoimages.


Fig.3 Production flow chart (Interpretation of flood areas)
*PFM (Pasco Fresh Map) is 25,000 scale vector map including river, road, boundary, etc.
**PSO (PASCO Satellite Ortho) is 25,000 scale cloud free satellite colour image

4) Change detection of inundated areas (Within 1st month)
Daily reporting of inundated areas was requested by Ministry of Land, Infrastructure, Transport and Tourism for their drainage efforts.


Fig.4 nundation monitoring using TerraSAR-X
To this end, TerraSAR-X images acquired on March 13, March 24, and April 4 were utilised.

This automatic change detection method utilises the characteristics of weak microwave reflection at the smooth surface (Fig.4). In Fig.4, yellow, pink and light blue areas indicate estimated flooded areas on March 13, 24 and April 4 respectively. The 2.5m pan-sharpened colour image from ALOS (PSO), acquired before the earthquake was utilised as the background reference.

5) High resolution panoramic oblique photo (after 1st month)
Using a special device handy digital camera on the helicopter, over 20,000 oblique photos were taken within several days and combined to make the panoramic images by each districts. Its resolution is sub centimetre, so these panoramic images are useful for damage estimation of houses, buildings, roads and any other properties. These oblique image archives would be valuable as well as orthoimages for reconstruction planning by local governments, ministries and academics.


Fig.5 Panoramic oblique photo (Onagawa city, Miyagi Pref.)
Quick delivery
The maps were delivered to the ministries and local governments directly within a few hours or within a day. Publishing the information on the PASCO website as free access has been ongoing. These contents and analyses data were feature in major papers, magazines and other media.

Conclusion
Disaster monitoring were provided within the shortest period of time, which could help to supply better disaster mitigation and restoration during the early stage of the huge disaster. Multi-source and multi-temporal data were essential to monitor the wide areas. To urgent processing of data, automatic change detection method was effective. Also, photogrammetry, field survey and visual check ensure the accuracy. Quick delivery to disaster management organization was important by any means through website, FTP and hand-carry within a few hours or within a day. The analysis results were provided in the form of user-friendly. We believe that, those maps and analyses would be useful for planning the reconstruction of damaged areas and recovery from the disaster even more.

Acknowledgements
We would like to express special thanks to contribute as follows; PRISM and AVNIR- 2(ALOS) from JAXA, WorldView-1,2 from Hitachi Solutions and DigitalGlobe, SPOT-5 from Astrium Geo-information, and RapidEye from RapidEye AG and Panaxx.

References

  • Okajima, Y., Yoshikawa and Shibayama, 2011, Recent experiences utilizing TerraSAR-X for the monitoring of natural disasters in different parts of the world, 2011 The IEEE Geoscience and Remote Sensing Society, Vancouver, FR3.T06.5
  • PASCO disaster monitoring project team, 2011, Addressing Natural Land -threat of the Nature, PASCO
  • Takagishi,S.,Hiramatsu and Kato, 2011a, In: High Resolution Satellite Remote Sensing Concerning the 2011 off the Pacific coast of Tohoku Earthquake and Tsunami Disaster edited by Scientific Research Working Group, The Journal of the Remote Sensing Society of Japan, Vol.31, No3 (2011) ,pp351,pp361-363
  • Takagishi, S., Yoshikawa and Shibayama, 2011b, Disaster monitoring by multi-temporal images of the 2011 Tohoku Earthquake and Tsunami, 2011 The IEEE Geoscience and Remote Sensing Society, Vancouver, TH4.T07.5.
  • Takagishi S., 2011c, DISATER MONITORING BY MULTI-TEMPORAL AND MULTISOURCE DATA FOR THE GREAT EAST JAPAN EARTHQUAKE AND TSUNAMI, The 32nd Asian Conference on Remote Sensing, TAIPEI, Sentinel Asia Special Session.
  • Yoshikawa,K., 2011, Monitoring of inundated area of the Great East Japan Earthquake by High resolution X band satellite images, Journal of the Japan Society of Photogrammetry and Remote Sensing, Vol.50,No.30(2011), pp. 122-123.

Note: This paper was originally published online at www.fig.net and presented at the FIG Working Week 2012 in Rome, Italy.