noun
microearthquake
Technical term in seismology for a very small earthquake, typically below magnitude 2.0 and not felt by people.
この地域では微小地震が頻繁に観測されている。
Microearthquakes are frequently observed in this region.
General term for earthquake; 微小地震 specifically refers to very small, often imperceptible earthquakes.
Compound of 微小 (びしょう, 'minute, microscopic') and 地震 (じしん, 'earthquake').