A sign of the landslide disaster is easily detected. A model learning unit (120) of an anomaly detection device (100) learns a relational expression between vibration strengths at frequencies based on a time series of frequency characteristics of a vibration strength detected during a learning period by a vibration sensor placed on a monitoring target. The anomaly detection unit (140) learns a relational expression between vibration strengths at frequencies based on a time series of frequency characteristics of a vibration strength detected during a new period by the vibration sensor. Then, the anomaly detection unit (140) determines whether or not there is an anomaly in the monitoring target based on a relational expression related to a new frequency, which is different from the relational expression learned during the learning period.
Please help me write a proper abstract based on the patent claims. CLAIM: 1. An information processing device comprising: a learning unit that learns a relational expression between vibration strengths at different frequencies based on a time series of frequency characteristics of a vibration strength detected during a learning period by a vibration detector placed on a monitoring target; and an anomaly detection unit that learns a relational expression between vibration strengths at different frequencies based on a time series of frequency characteristics of a vibration strength detected during a new period by the vibration detector, and determines whether or not there is an anomaly in the monitoring target based on a relational expression related to a new frequency, which is different from the relational expression learned during the learning period. 2. The information processing device according to claim 1, wherein each of the learning unit and the anomaly detection unit learns a relational expression between vibration strengths at different resonance frequencies. 3. The information processing device according to claim 1, wherein the anomaly detection unit extracts the relational expression related to a new frequency which is higher than frequencies related to the relational expressions learned during the learning period, from the relational expressions learned during the new period, as the relational expression related to the new frequency. 4. The information processing device according to claim 1, wherein the anomaly detection unit determines whether or not there is an anomaly in the monitoring target based on the new relational expression in a case that the time series of the frequency characteristics of the vibration strength detected during the new period does not satisfy a relation represented by the relational expression learned during the learning period. 5. The information processing device according to claim 1, wherein the anomaly detection unit determines that there is an anomaly in the monitoring target in a case that number of the new relational expressions is equal to or larger than a predetermined threshold value. 6. The information processing device according to claim 1, wherein the vibration detector detects vibration generated by raindrops falling on the monitoring target. 7. An anomaly detection method comprising: learning a relational expression between vibration strengths at different frequencies based on a time series of frequency characteristics of a vibration strength detected during a learning period by a vibration detector placed on a monitoring target; and learning a relational expression between vibration strengths at different frequencies based on a time series of frequency characteristics of a vibration strength detected during a new period by the vibration detector, and determining whether or not there is an anomaly in the monitoring target based on a relational expression related to a new frequency, which is different from the relational expression learned during the learning period. 8. The anomaly detection method according to claim 7, wherein, in the learning a relational expression, a relational expression between vibration strengths at different resonance frequencies is learned. 9. A non-transitory computer readable storage medium recording thereon a program, causing a computer to perform a method comprising: learning a relational expression between vibration strengths at different frequencies based on a time series of frequency characteristics of a vibration strength detected during a learning period by a vibration detector placed on a monitoring target; and learning a relational expression between vibration strengths at different frequencies based on a time series of frequency characteristics of a vibration strength detected during a new period by the vibration detector, and determining whether or not there is an anomaly in the monitoring target based on a relational expression related to a new frequency, which is different from the relational expression learned during the learning period. 10. The non-transitory computer readable storage medium recording thereon the program according to claim 9, wherein, in the learning a relational expression, a relational expression between vibration strengths at different resonance frequencies is learned.