What type of plate boundary has a lot of seismic activity

I'd have to say the Southern Eurasian plate and the Western part of "our" North American plate (mainly around California) both have a lot of above sea level activity. The most activity below or right at sea level would possibly be the Philippines plate.

Destructive plate boundaries / conservative boundaries, but destructives boundaries are the worse because volcanoes and earthquakes occur here. The collision of the 2 plates create tension and release seismic waves, also because of this the oceanic plate is dragged downwards (subduction) creates a ocean trench, as it sinks it melts and creates magma, this is leeds to volcanoes erupting