Earthquake Engineering

Magnitude

an estimate of total energy released during the earthquake event, often given by the Richter magnitude

Intensity

a measure of the shaking at a given site, sometimes presented in terms of observed damage/s

Hypocenter

the point inside the earth where the earthquake started; also called FOCUS; defined by latitude, longitude, and depth below the surface

Epicenter

the point on the surface of the earth directly above the hypocenter/focus

Vertical Structural Irregularities

1. Stiffness Irregularity

2. Weight (Mass) Irregularity

3. Vertical Geometric Irregularity

4. In-Plane Discontinuity in Vertical Lateral-Force-Resisting Element Irregularity

5. Discontinuity In Capacity

Stiffness Irregularity - Soft Storey

one in which the lateral stiffness is less than 70% of that in the storey above or less than 80% of the average stiffness of the 3 stories above

Weight (Mass) Irregularity

shall be considered to exist where the effective mass of any storey is more than 150% of of the effective mass of an adjacent storey. A roof that is lighted than the floor below need not be considered.

Vertical Geometric Irregularity

shall be considered to exist where the horizontal dimension of the lateral-force-resisting system in any storey is more than 130% of that in an adjacent storey. One-storey penthouse need not be considered.

In-Plane Discontinuity in Vertical Lateral-Force-Resisting Element Irregularity

an in-plane offset of the lateral-load-resisting elements greater than the length of those elements

Discontinuity in Capacity - Weak Storey Irregularities

one in which the storey strength is less than 80% of than in storey above. The storey strength is the total strength of all the seismic-resisting elements sharing the storey for the direction under consideration.