I agree with most of the poster here - the river is a truly significant barrier, and it might be worse after an earthquake and during the inevitable aftershocks. Most likely the wisest course will be to hunker down, using the abundant food and comfortable camping gear you can carry in the car. This goes double if you are not alone, and have to consider traveling over that terrain with your family.

If alone, consider carefully chosen, lightweight backpacking gear as the core of your outfit. Drive as far as you can in the car and then transition to a mountain/touring bike carrying your gear, which will probably weigh in the neighborhood of forty/fifty pounds including food for two weeks.

The bicycle vastly increases your range, if you can get it over the bridges and through or around the tunnels. It is no trick at all to travel 50-70 miles per day with a fully loaded touring bike, so it might be worthwhile to portage around obstacles in two or more stages if you will then reach clear roads or trails.

If that doesn't work, you are down to your backpacking outfit. Keep it small and as light as possible. Again, for a fit, experienced hiker, the distance you will need to trek is perfectly feasible. For sustenance,go with freeze dried stuff, especially since you have abundant water - MREs are way too heavy.

I would spend some time investigating trail networks in the area that might serve as alternatives if the roads are blocked. Google Earth is a fantastic resource here.

Overall, keep your options open. Stock your vehicle with versatile gear. Thee is always the possibility, I take it, that the focal point of the emergency might be at your "away"location and that you might be occupied there for a considerable time.

You might consider looking carefully at the geology of this region, especially with regard to the location of faults and any earthquake history. That information will help you refine possible scenarios.

Again, it is likely that your most reasonable option will be to shelter in place. Opening the transportation arteries will be a fairly high priority once rescue/recovery efforts are underway.

Whatever happened to "Beam me up, Scotty!"?