Masonry Magazine December 1994 Page. 27
Instrumentation in Santa Monica
Instrumentation in Santa Monica, 14.3 miles (23 km) from the epicenter, recorded a horizontal acceleration of 0.93 g and a vertical acceleration of 0.25 g. At this significant distance, the ground motion was over three times code design standards. This was a very powerful earthquake! According to seismologists, the ground accelerations were the highest ever recorded.
The Northridge Mall
The Northridge Mall, which is less than 3 miles (4.5 km) from the epicenter, suffered extensive damage. The Bullocks Store, a non-masonry structure, collapsed. Yet only a few yards away, the Broadway Store, a double wythe reinforced brick facade with concrete floors and interior concrete columns stood like a fortress. There was extensive damage to the interior and exterior, but it is repairable. Ironically, the Broadway Store was under construction during the 1971 San Fernando Earthquake.
Fire Stations
Fire Stations, which use extensive masonry in their design, withstood the earthquake almost flawlessly. The facilities were in full operation the same day of the earthquake.
Typical Fire Station Perimeter Wall
Typical Fire Station perimeter wall with no damage.
Broadway, Northridge Mall
Broadway, Northridge Mall is double wythe reinforced brick and shows damage from floor pounding while adjacent Bullock's Store (not masonry) collapsed.
Masonry Construction
The technology in the fields of concrete and structural steel has advanced at a pace never before known to man. On the other hand, masonry has been common for thousands of years, so the design of masonry has evolved empirically, which means that what has worked successfully for thousands of years should work successfully in the future. Masonry construction has been enhanced by the use of reinforcement within the masonry unit, thereby giving masonry additional capability to withstand lateral seismic and wind forces.
8.3 San Francisco
8.3 San Francisco
April 18, 1906
6.8 Northridge
6.8 Northridge
January 17, 1994
7.7 Tehachapi
7.7
Tehachapi
July 21, 1952
7.4 Landers
7.4 Landers
June 28, 1982
7.1 Loma Prieta
7.1 Loma Prieta
October 17, 1989
6.5 Sylmar
6.5 Sylmar
February 9, 1971
6.5 Big Bear
6.5 Big Bear
June 28, 1982
6.1 Joshua Tree
6.1 Joshua Tree
April 22, 1992
5.9 Whittier
5.9 Whittier
October 1, 1987
5.8 Sierra Madre
5.8 Sierra Madre
June 28, 1991
6.3 Long Beach
6.3 Long Beach
March 10, 1933
5.0-5.9 Earthquake Effects
5.0-5.9 Felt by all People walk unsteadily, Glass breaks. Furniture moves. Objects fall from shelves.
6.0-6.9 Earthquake Effects
6.0-6.9 Difficult to stand. Serious damage to unreinforced chimneys, stucco and unreinforced masonry walls.
7.0-7.9 Earthquake Effects
7.0-7.9 Some well built wooden structures and bridges destroyed serious damage to dams, dikes embankments, Large land-slides.
8.0 Earthquake Effects
8.0 Damage nearly total. Large rock masses displaced. Lines of sight and level distorted. Objects thrown into air.