Information for Strong-Motion Station
San Francisco - City Hall
CGS - CSMIP Station 58789
Earthquakes recorded by this station
(Station Photograph - click to enlarge)(Sensor Layout - click to see PDF File)
Latitude 37.7788 N
Longitude 122.4193 W
Elevation (m) 20
Site Geology Alluvium over rock (Franciscan)
Vs30 (m/sec) 286 (inferred)
Site Class D
Remarks/Notes Site information sources
No. of Stories above/below ground5/0
Plan ShapeRectangular
Base Dimensions309' x 408'
Typical Floor DimensionsRectangular 280' x 408'
Design Date1912 (1997 Retrofit)
Instrumentation2001. 18 accelerometers, on 5 levels in the building.
Vertical Load Carrying SystemConcrete slabs on steel frames with masonry infill walls. Steel dome is supported by steel columns which are supported by dome support towers at the corners of the rotunda.
Lateral Force Resisting SystemOriginal building had steel frames infilled with unreinforced brick masonry and hollow clay tiles. Building was retrofitted by strengthening the superstructure with concrete shear walls and adding base isolators.
Foundation TypeIn original building, steel columns were supported by isolated spread foodings. During the retrofit, the footings were tied together by concrete grade beams.
RemarksThe building suffered damage during the 1989 Loma Prieta earthquake and was strengthened in 1997-98.