Ligo Can't See Gravitational Waves From Black Hole Mergers

Ligo was designed to see gravitational waves from black hole mergers, but only the last few seconds of them. So why can ligo not see gravitational waves that are longer? The problem is sismic noise. The earth itself is shaking more loudly than those gravitational waves. Lisa would be much more powerful, much more sensitive and able to hear gravitational waves at longer frequencies. But again, that's expensive, and that's far off in the future. And so until then, people are thinking, do we need to build our own gravitational wave detectors, or can we find one already existing in the galaxy? Can we use the galaxy itself as a gravitational wave detector? And the answer