Earthquake Engineering Research - HKU Libraries - The University ...

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Number of Pixels
(Frequency)
Threshold (p>99 5%)
Estimated
damaged areas
Normal distribution
based on sample
ixels
Difference of digital numbers (change of brightness)
Figure 1:
estimation
Flowchart of damaged area
Figure 2:
estimation
Criteria of damaged area
3. NEW ESTIMATION METHOD BASED ON TIME-SERIES IMAGES
Some problems shown in the followings remain in the estimation results based on two images before
and after earthquake.
a) Cloud influence remains even if Stable Light Image is applied.
b) Reflection of water area leads to mis-judgment
c) Small cities are neglected due to the variance of the night light
These problems would be resolved, if pixel-based average and standard deviation of digital number
were analyzed for several images before an earthquake and significant test were applied to post-event
image. This procedure is called "Time-Series Images Method". It takes about 10 hours to complete
analysis using more than 30 images. It is important to notice that the gain of the sensor estimated
originally affects the results in the period that moon light is bright. So it is better to use images in
about 10 days before and after new moon. As this method is operated manually now, automated
system for this method should be built.
4. APPLICATION OF BASIC METHOD TO THE TURKEY MARMARA EARTHQUAKE
DISASTER
We estimated the possible impacted areas of the 1999 Marmara Earthquake Disaster that occurred in
northwest Turkey on August 17. The DMSP/OLS images in this region were provided from National
Oceanic and Atmospheric Administration's National Geophysical Data Center (NOAA/NGDC). The
nighttime images before and after the earthquake are shown in Figures 3 and 4 respectively.
Fortunately, the two images have little cloud influence considering the TIR images (Figures 5 and 6).
The histogram of digital number differences between two VNIR images is shown in Figure 7.
The estimated impacted areas spread widely in Yalova, Kocaeli and other provinces (Figure 8). These
estimation results showed with a high degree of correspondence with the real damages.