Design Earthquakes – Definitions

For Concrete Structures: OBE (operational basis earthquake) = 144-yr Return Period (50 percent chance of being exceeded in 100 years).

Max. Design EQ: for Structures Defined As Critical use MCE, In general for other structures, MDE = 950-yr return period (10 percent chance of being exceeded in 100 years).

MCE is defined as the greatest earthquake that can reasonable be expected to be generated by a specific source (which comes from a deterministic site hazard analysis).

USACE references: Stability Analysis of Concrete StructuresEarthquake Design and Evaluation of Concrete Hydraulic StructuresEarthquake Design and Evaluation for CW ProjectsSafety of Dams – Policies and Procedures.

Dams Under State Jurisdiction – CAL DSOD

Dams that fall under State jurisdiction are subject to: Statutes and Regulations Pertaining to Supervision of Dams and Reservoirsby the California Division of Safety of Dams (DSOD).  Dam height (in feet) is measured from the downstream toe to the maximum storage elevation/spillway. Storage capacity is in the units of acre-feet.


Division of Safety of Dams.

1 foot (ft) = 0.3048 meters (m), 1 acre-foot (ac-ft) = 1233.5 cubic meters (m^3)