Most issues of earthquake safety are site specific. Except for landfill which is inherently problematic most concerns are structural or particular to a specific site - like slumping and sliding which is common in the Coast Range.
When you decide to buy you should have inspections at your expense that can reveal problems. If negotiations can not resolve differences you may have to bear those costs as the deal falls apart.
Below is an excellent primer about buying real estate that will address most questions that pop up. Take time to interview agents, they are NOT interchangeable.