[GOP_1900AD]

San Mateo county, 3rd floor of early 1990s office building, built on slab foundation on deep piers driven into former salt evaporater / dried out bay mud. Felt two rollers, enough to rattle windows but not enough to cause building to creak and groan. Was on con call w/ folks in Alameda County who said they did not detect it. Some newbies were freaking out and running into hallway. That's about it.

[underwiredsupport]

AFTERSHOCK!!

Magnitude 5.0 - CENTRAL CALIFORNIA
2004 September 28 17:19:07 UTC

Preliminary Earthquake Report
California Integrated Seismic Net
USGS/ Caltech/ CGS/ UCB/ UCSD/ UNR
 

 

A moderate earthquake occurred at 17:19:07 (UTC) on Tuesday, September 28, 2004. The magnitude 5.0 event has been located in CENTRAL CALIFORNIA. The hypocentral depth was poorly constrained. (This is a computer-generated message -- this event has not yet been reviewed by a seismologist.)

 

 

 

Magnitude	5.0
Date-Time	Tuesday, September 28, 2004 at 17:19:07 (UTC) = Coordinated Universal Time Tuesday, September 28, 2004 at 10:19:07 AM = local time at epicenter
Location	35.826°N, 120.453°W
Depth	2.5 km (1.6 miles) (poorly constrained)
Region	CENTRAL CALIFORNIA
Distances	8 km (5 miles) SSW (193°) from Parkfield, CA 20 km (12 miles) NNW (340°) from Shandon, CA 23 km (14 miles) ENE (69°) from San Miguel, CA 30 km (19 miles) NE (42°) from Paso Robles, CA 212 km (132 miles) SE (142°) from San Jose City Hall, CA
Location Uncertainty	horizontal +/- 0.9 km (0.6 miles); depth +/- 4.3 km (2.7 miles)
Parameters	Nst= 38, Nph= 38, Dmin=5 km, Rmss=0.6 sec, Gp= 65°, M-type=local magnitude (ML), Version=2
Source	California Integrated Seismic Net USGS/ Caltech/ CGS/ UCB/ UCSD/ UNR
Event ID	nc51147893

 

 

[ravinson]

early 1990s office building, built on slab foundation on deep piers driven into former salt evaporater / dried out bay mud.

Keep in mind that those piers are supposed to be driven deep enough to go through the mud and into the solid rock below.