Seismic sensor and earthquake determination method

An earthquake determination method comprising:

• shifting to a measurement mode from a standby state when an acceleration larger than a threshold is measured by a measurement unit in the standby state.
• calculating an index value indicating a scale of an earthquake based on the acceleration measured in an earthquake processing period starting after a predetermined period has elapsed after shifting to the measurement mode,
• wherein when it is determined that an earthquake of a certain magnitude or larger or a vibration larger than an estimated strength is occurred in the earthquake processing period, a shut-off signal for shutting off an operation of a related device is output, the earthquake determination method further comprising:
• a continuous earthquake determination step of determining whether or not an earthquake has occurred, based on the acceleration measured in the earthquake processing period,
• a shut-off determination step of determining as to whether the measured acceleration is due to an earthquake or noise, and outputting the shut-off signal when it is determined that the earthquake has occurred, and inhibiting output of the shut-off signal when it is determined that the measured acceleration is due to noise.