**6.1 Selection of the target area**

Three conditions must be met to apply methods for earthquake observation from social media.

The first is that a sufficient number of people use Twitter in a targeted area. The second one is that several earthquakes occur each year for a target area. The third one is that infrastructure should be set up in a target area.

These three conditions are needed in each step of earthquake detection and location estimation. A sufficient number of tweets and a certain number of earthquakes are needed to create a classifier for tweets and to estimate the locations of earthquake epicenters. Accurate logs of earthquakes are also necessary to calculate the false-alarm probability of social sensors and to evaluate the earthquake detection system performance.

If creating a classifier and setting a trigger for earthquake detection in an area and applying them in another area, then the third condition is not indispensable. However, the first condition and the second condition are necessary in both areas.

Fig. 14. Twitter user map.

Fig. 15. Earthquake map.

20 Will-be-set-by-IN-TECH

In this section, we explain how to evaluate results of experiments and describe points that

Three conditions must be met to apply methods for earthquake observation from social media. The first is that a sufficient number of people use Twitter in a targeted area. The second one is that several earthquakes occur each year for a target area. The third one is that infrastructure

These three conditions are needed in each step of earthquake detection and location estimation. A sufficient number of tweets and a certain number of earthquakes are needed to create a classifier for tweets and to estimate the locations of earthquake epicenters. Accurate logs of earthquakes are also necessary to calculate the false-alarm probability of social sensors

If creating a classifier and setting a trigger for earthquake detection in an area and applying them in another area, then the third condition is not indispensable. However, the first

**6. Evaluation and application**

**6.1 Selection of the target area**

should be set up in a target area.

Fig. 14. Twitter user map.

Fig. 15. Earthquake map.

should be considered when applying these methods.

and to evaluate the earthquake detection system performance.

condition and the second condition are necessary in both areas.

Figure 14 depicts the Twitter user distribution map and Fig. 15 depicts an earthquake occurrence distribution map. Earthquake detection using information from Twitter users is applicable in overlapping areas of these two maps: for example, Japan, the west coast of the U.S., Indonesia, Turkey, Iran, and Italy.

The number of Twitter users has been increasing continuously. Therefore, those areas can probably be expanded. Additionally, if one uses social media other than Twitter, then overlapping areas might be changed.

Therefore, a target area should be chosen very carefully to apply the methods described in this chapter.
