severe earthquake; strong earthquake
Refers to an earthquake of high intensity, typically used in news reports and seismology. In Japan's seismic intensity scale, it corresponds to upper 5 (強) or higher.
A strong earthquake struck the Tohoku region last night.
Secure your furniture in preparation for a severe earthquake.
強震 is the intensity level just below 烈震 on the old JMA scale, so learners easily mix up which term denotes the stronger quake.
Compound of 強 (strong) and 震 (earthquake).