The phrase "massive quake" means a very strong and powerful earthquake. It refers to a sudden shaking or trembling of the ground that is extremely intense and can cause a lot of damage. Full definition
Tanaka saw the same signal in the run - up to two nearby massive quakes in 2005 and 2007 (Geophysical Research Letters, DOI: 10.1029 / 2009GL041581). (newscientist.com)
Earthquakes occurring today in the New Madrid Seismic Zone (center of image; red dots denote quakes greater than magnitude 3 that have occurred since 1974) are not aftershocks of massive quakes that occurred in the winter of 1811 to (sciencemag.org)
That's because at seismometers closer to a massive quake's epicenter, the slowly moving vibrations of typical seismic waves often arrive at instruments before Earth's tectonic slabs have stopped shifting, thus masking the signals generated by the temblor's final spasms. (sciencemag.org)