earthquake resistant design
EARTHQUAKE
An earthquake (also known as a tremor, temblor or seismic activity) is the result of a sudden release of energy in the earth’s crust that creates SEISMIC WAVES. Earthquakes are measured with a seismometer; a device which also records is known as a seismograph.
SEISMIC DEFORMATION
When an earthquake fault ruptures, it causes two types of deformation: static; and dynamic. Static deformation is the permanent displacement of the ground due to the event. The earthquake cycle progresses from a fault that is not under stress, to a stressed fault as the plate tectonic motions driving the fault slowly proceed, to rupture during an earthquake and a newly-relaxed but deformed state.
Typically, someone will build a straight reference line such as a road, railroad, pole line, or fence line across the fault while it is in the pre-rupture stressed state. After the earthquake, the formerly stright line is distorted into a shape having increasing displacement near the fault, a process known as elastic rebound.
SEISMIC WAVES
The second type of deformation, dynamic motions, is essentially sound waves radiated from the earthquake as it ruptures. While most of the plate-tectonic energy driving fault ruptures is taken up by static deformation, up to 10% may dissipate immediately in the form of seismic waves.
The mechanical properties of the rocks that seismic waves travel through quickly organize the waves into two types. Compressional waves, also known as primary or P waves, travel fastest, at speeds between 1.5 and 8 kilometers per second in the Earth's crust. Shear waves, also known as secondary or S waves, travel more slowly, usually at 60% to 70% of the speed of P waves. P waves shake the ground in the direction they are propagating, while S waves shake perpendicularly or transverse to the direction of propagation.
Although wave speeds vary by a factor of ten or more in the Earth, the ratio between the average speeds of a P wave and of its following
An earthquake (also known as a tremor, temblor or seismic activity) is the result of a sudden release of energy in the earth’s crust that creates SEISMIC WAVES. Earthquakes are measured with a seismometer; a device which also records is known as a seismograph.
SEISMIC DEFORMATION
When an earthquake fault ruptures, it causes two types of deformation: static; and dynamic. Static deformation is the permanent displacement of the ground due to the event. The earthquake cycle progresses from a fault that is not under stress, to a stressed fault as the plate tectonic motions driving the fault slowly proceed, to rupture during an earthquake and a newly-relaxed but deformed state.
Typically, someone will build a straight reference line such as a road, railroad, pole line, or fence line across the fault while it is in the pre-rupture stressed state. After the earthquake, the formerly stright line is distorted into a shape having increasing displacement near the fault, a process known as elastic rebound.
SEISMIC WAVES
The second type of deformation, dynamic motions, is essentially sound waves radiated from the earthquake as it ruptures. While most of the plate-tectonic energy driving fault ruptures is taken up by static deformation, up to 10% may dissipate immediately in the form of seismic waves.
The mechanical properties of the rocks that seismic waves travel through quickly organize the waves into two types. Compressional waves, also known as primary or P waves, travel fastest, at speeds between 1.5 and 8 kilometers per second in the Earth's crust. Shear waves, also known as secondary or S waves, travel more slowly, usually at 60% to 70% of the speed of P waves. P waves shake the ground in the direction they are propagating, while S waves shake perpendicularly or transverse to the direction of propagation.
Although wave speeds vary by a factor of ten or more in the Earth, the ratio between the average speeds of a P wave and of its following