Hi Kiddo. It’s kind of strange you should mention the San Jose quake. This quake isn’t to far from the 1984 Morgan Hill quake.

The magnitude 6.2 Morgan Hill earthquake that damaged the San Jose area on April 24 caused the strongest horizontal earthquake acceleration ever measured. The California Department of Conservation’s Division of Mines and Geology (CDMG) recorded the measurement of a shaking force one and a third times the force of gravity (1.3g) on a strong-motion recorder at Coyote Dam, 17 miles south of the epicenter near Mount Hamilton.

Seismologic theory has predicted an energy-concentration effect called "directivity focusing" which states that an earthquake's force may be concentrated in a particular direction, rather than pulsing equally in all directions. The data from this earthquake may represent the first measurement of that effect, with 1.3g shaking 17 miles south of the epicenter, and only 0.3g at Halls Valley, just two miles north.

The most dramatic effect was near Morgan Hill, where damage consisted of houses falling off unbraced crippled foundations and incaving of stream banks. Morgan Hill is located 20 km (12 miles) south of the epicenter of the main shock, but only 3 km (2 miles) west of the zone of aftershock epicenters. This is because the aftershock zone propagated some 25 km southeastward along the Calaveras fault from the main shock epicenter.

The southeastern end of the 1984 Morgan Hill aftershock zone coincided with the epicenter of the 1979 Coyote Lake earthquake. The aftershock zone of the 1979 earthquake also extended to the southeast of its main shock. During the 1979 and 1984 earthquake sequences, the Calaveras fault zone ruptured in the subsurface along a total length of 45 km extending to the southeast from Mt. Hamilton. This rupture occurred mainly at earthquake depths of 1 to 10 km below the surface, according to focal depths determined by the USGS.

If memory serves me correctly there was acceleration in creep that lasted for 11 weeks before the 1984 quake. This was seen in the San Juan Bautista area. This also brings to mind that there was acceleration in creep in the Parkfield area before the last two quakes in that area. With one of the quakes this acceleration was seen in San Juan Bautista at 3 different locations at the same time as it was seen in Parkfield.

If only to understand what I know. Maybe later. Take Care...Cowboy