An aseismic ridge is "a long, linear and mountainous structure that crosses the basin floor of some oceans." They do not cause earthquakes.
It is called an "aseismic ridge" because they do not receive seismic activity. As a result, they tend to be stable. They are in length.
Aseismic ridges going towards subduction zones can impact the process of subduction, causing a phenomenon known as flat slab subduction.
Examples
Atlantic Ocean Walvis Ridge
Indian Ocean Eighty Five East Ridge Ninety East Ridge
Pacific Ocean Carnegie Ridge
See also Mid-ocean ridge
References