October 17, 1989 - 5:04 pm local time
Many folks in Santa Cruz and the surrounding San Francisco Bay Area will remember this date for quite some time. Some were just getting home for the day, some were shopping in downtown Santa Cruz, and many were watching the World Series when a ~7M earthquake jolted through the area. This was the first major earthquake to occur along the San Andreas Fault zone since the 1906 San Francisco quake. Sixty-three people died and thousands were injured. At the time, it was said to be the costliest natural disaster in the U.S.
The hypocenter, or focus, is the point within the Earth where an earthquake rupture originates. The epicenter is the point directly above it at the surface of the Earth. The Loma Prieta earthquake is officially recorded by the U.S. Geological Survey at N 37.036, W 121.883 with a focus depth of 10.43 mi.
The epicenter’s location is in a remote area of the Forest of Nisene Marks State Park in the Santa Cruz Mtns. If the winter gate is open, you can begin this hike by parking at the Porter Family Picnic Area. If the gate is closed for the winter, you will need to park at the George’s Picnic Area, which adds an additional 2.2 mi round-trip distance to the hike. The remaining distances described here are from the Porter parking. Follow the Aptos Creek Fire Road uphill approximately 1.5 mi until you see a sign for the trailhead to the Aptos Creek Trail. If you rode your bike, park it here at the bike racks as they are only allowed on the Fire Road. The epicenter and cache are located approximately 0.6 mi east along the Aptos Creek Trail. There are a couple of rock-hopping creek crossings you will make – a hiking staff is advised (I use two). Along the way you will see evidence of slumps and scars from landslides triggered by the earthquake. Many of the deadfall trees you see were caused by the ground shaking during the earthquake. Since the GPS reception is very poor to non-existent here, you should follow these directions: the cache is located past the sign the State Park placed to mark epicenter, approximately 200 yds or so (I counted 350 Coralgeo steps) further along the trail. From a prominent crest in the trail, look at the ancient slump scar to the left (uphill). About 10 yds off-trail, a small cluster of trees hides a hollow stump. Round-trip hike approximately 4 mi.
OPTIONAL HIKE EXTENSION (add another star to the terrain rating) - Continue along the Aptos Creek Trail for nearly 2 mi until it intersects with the Big Slide Trail. Although strenuous, this rugged 1.5 mi section of trail will take you up through a “drunken forest” before connecting back up to the Aptos Creek Fire Road. Here the trees have twisted and bent trunks from attempting to grown back into a vertical position after the ground rotated and slumped beneath them. Along the Big Slide Trail you will see more landslide slumps and scars, fractures in the ground, and a marshy sag pond. Sag ponds form when the Earth’s surface stretches due to tectonic movement and “sags”, or creates a depression that can fill in with rainwater. In the Santa Cruz Mtns. these are usually seen as boggy wet marshes during the rainy season, and drier ponds during the summer. Over time these depressions fill in with sediment and vegetation through natural processes until a state of equilibrium is once again reached. Heading downhill along the fire road back to your starting location, you will travel from the Top of the Incline to the Bottom of the Incline like the men during the historic lumbering era. If you look closely you can see where they slid the huge logs down the slope. Round trip hike approximately 11 mi.
ADDENDUM - This is the first cache in this State Park, and the first in the Song and Dance series of caches. The original cache was a plastic container that included among other things a mystery novel entitled Fault Lines by Sarah Andrews (formerly of the USGS) and some materials on the shaking intensity that was felt at this location in 1989 and 1906, hence the name... shake, shake, shake... shake, shake, shake... shake your bootie... shake your bootie. Four years later, on Memorial Day 2005, I upgraded the container to a .50 cal ammo can and restocked some of the goodies. Please try to keep your trades in the "worthy" catagory, because after hiking this far and actually finding the cache, you deserve it!
Other caches in the Song and Dance series include: