The Tsunami Harddisk Detector is a small software client (see Fig. 1) installed on your computer which continuously monitors the vibration of the internal components of your harddisk (see Fig. 2). Since they are extremely fragile, they react to any accelerations of the computer, including those that originate from earthquakes. Different technical strategies are currently under investigation to analze seismic activity. For best performance, the computer with its harddisk should be fastened to the ground.

Fig. 1: Mainwindow of the software client application.

One computer is not enough to identify the epicenter of an earthquake. However, a small number of networked computers can locate the epicenter, measure the intensity and estimate the risk of a tsunami. To this end, the computers are connected via a P2P network. To organize the communication within the network, it consists of many nodes (which perform sensing) and a few supernodes (which perform signal processing). In particular, the supernodes perform two tasks:

• locate the epicenter based on the time lag and intensity of the event
• remove ‘signal noise’. Noise is generated by events that shake the harddisk, but can not cause a tsunami (e.g. a user kicks his computer). The supernode can detect this noise because it is improbable that many users kick their computer simultaneously.

In order to be able to locate the epicenter, each node must know exactly where it stands on earth. Therefore, the longitude and latitude as well as the orientation must be entered when the software is started the first time. This data can be obtained from an attached GPS-mouse or from www.gpsvisualizer.com.

Although the described method works in principle, it has inherent problems: the internals of harddisks operate at very high speeds with frequencies of about 1 kHz, while earthquakes exhibit much smaller frequencies (see the seismogram to the right). Also the accelerations during normal harddisk operation are about 30 g, while an earthquake has a much smaller horizontal acceleration (for example the Kobe earthquake in 1995 had 0.84 g horizontally). Hence, the waves resulting from earthquakes must be filtered out from other waves.