At San Leandro Chabot Park, which is actually located in Oakland at the very end of San Leandro’s Estudillo Avenue (I know this is confusing), there is a line of railroad spikes driven into the pavement of the road leading up to the Lake Chabot Dam. I counted 47 of them, but I could have missed some at either end. They appear to be 20 feet apart, so if there are 50, that would make 1000 feet. Anyway, they are perfectly aligned and extend across the Hayward fault trace. Someone periodically surveys them, I’m sure. But after the next big quake, someone will check them rather soon and then again, often, because movement on a fault doesn’t end with an earthquake. There is very often a postseismic creep that continues to displace the land along a fault, which is of interest to seismologists.