Earthquake alert is an alert application which detects earthquake via the device's accelerometer.
In the settings of the app you can set the sensor's sensitivity. If you set it to high it will detect the smallest quakes too.
To activate the alarm just tap the Activate alarm icon and set a countdown time. When the countdown is up the application will activate the sensor to detect the quakes.
To deactivate the alarm just tap the Deactivate alarm icon.