**7. References**


The authors would like to thank all of the team members who participated in the Wenchuan Earthquake Disaster Reconstruction, Monitoring and Assessment Using Remote Sensing

*This work was supported by the National Basic Research Program of China (2009CB723906,* 

Ainsworth T L, Schuler D L, Lee J S. Polarimetric SAR characterization of man-made

Chen Yuntai, Xu Lisheng, Zhang Yong et al., Report on the Wenchuan large earthquake

Cloude S R, Pottier E. A review of target decomposition theorems in radar polarimetry. IEEE

Cloude S R, Pottier E. An entropy based classification scheme for land applications of

Cui Peng, Wei Fangqiang, He Siming et al. 2008. Mountain disasters induced by the

Deng Qidong, Ran Yongkang, Yang Xiaoping. 2007. Active tectonic map of China. Beijing:

Ermini L. and Casagli N. 2003. Prediction of the behavior of landslide dams using a

F.Mattia, T.Le Toan, J. C.Souyris, G.D.Carolis, N.Floury,and F.Posa, The effect of surface

Fu Bihong, Shi Pilong, Zhang Zhilong. 2008. Spatial characteristics of the surface rupture

Guo H D, Liao J J,Wang C L et al. 1997. Use of multifrequency,multipolarization shuttle

Guo H D, Zhu L P,Shao Y et al. 1996. Detection of structural and lithological features

southern China. Journal of Geophysical Research, 101(E10): 23101-23108. Guo Huadong, Liu Hao, Wang Xinyuan, et al. 2000. Subsurface old drainage detection and

earthquake of May 12 in Wenchuan and the disasters mitigation. JOURNAL OF

geomorphological dimensionless index. Earth Surface Processes and Landforms,

roughness on multifrequency polarimetric SAR data . *IEEE Trans Geosci Rem. Sens.*,

rroduced by the MS 8.0 Wenchuan earthquake using high-resolution remote sensing imagery. ACTA GEOLOGICA SINICA, 82(12): 1679-1687(In Chinese) Ge Yong, Xu Jun, Liu Qingsheng, et al. 2009. Image interpretation and statistical analysis of

vegetation damage caused by the Wenchuan earthquake and related secondary

imaging radar for volcano mapping in the kunlun mountains of western China.

underneath a vegetation canopy using SIR-C/X-SAR data in Zhao Qing test site of

paleoenvironment analysis using spaceborne radar images in Alxa Plateau, Science

polarimetric SAR. IEEE Trans Geosci Rem Sens, 1997, 35: 68–78

structures in urban areas using normalized circular-pol correlation coefficients.

*2009CB723902) and National Natural Science Foundation of China (60972141).*

source of May 12, 208, http://www.csi.ac.cn/Sichuan

MOUNTAIN SCIENCE, 26(3):.280-282(In Chinese)

disasters. Journal of Applied Remote Sensing, 3, 031660.

Remote Sensing of Environment, 59:364-374.

in China Series D: Earth Sciences, 43(4): 439-448.

Rem Sens Environ, 2008, 112: 2876–2885

Trans Geosci Rem Sens, 1996, 34: 498–518

Earthquake Press (In Chinese)

vol. 35, no. 4, pp. 954−966, July 1997

28(1): 31-47.

**6. Acknowledgement** 

Technology.

**7. References** 


**0**

**15**

*Japan*

**Earthquake Observation by Social Sensors**

Many studies have examined observation and detection of earthquakes using physical sensors. These systems require highly accurate physical sensors located over a broad area,

Social media have garnered much attention recently and the number of social media users has been increasing. Social media are kinds of media for social interaction among users. Users create contents for themselves and exchange them on social media. Social media include many kinds of forms, including weblog, wikis, videos and microblogs. One of the biggest

Social media users often make posts about what happened around them: live performance, sports events and natural disaster, including earthquake. Figure 1 depicts the graph of tweet counts and the sizes of earthquake on March 11th 2011, the day of the Great Eastern Japan Earthquake. It is apparent that tweet counts and earthquake occurrences are correlated. It means that when earthquakes occurs, social media users make posts about those earthquakes. Along with the popularization of social media, new methods for earthquake observation are appearing. These method use information about earthquakes posted on the internet by users. For example, the web site *Did You Feel It?*, operated by the United States Geological Survey (USGS), gathers earthquake information from web-site users through a

Fig. 1. Size of earthquakes and change of tweet counts on the day of the Great Eastern Japan

necessitating great expense to set up the supporting infrastructure.

characteristics of social media is *user-generated contents*.

**1. Introduction**

Earthquake

Takeshi Sakaki and Yutaka Matsuo

*The University of Tokyo*

