Dear Sahand,

Would you please to take a look on https://en.wikipedia.org/wiki/Peak_ground_acceleration

Sir,

The classification of eartha quake is based on destruction, damage. It varies with the distance. Illustrate the process with the Markov chain model by taking analysis points as destruction, damage with respect to distance.

with regards,

R.V.S.Lalitha

thank u so much dear friends bec your attention

Hi Sahand

at the risk of stating the obvious, a quick comment. Earthquakes and ground motion are two different things that should not be confused. Magnitude e.g. describes the earthquake (source). PGA e.g. describes the effect of the earthquake at a certain distance from the source, on a certain kind of site (the same M6 event at 60 km could give very different ground motion inside a basin and outside it). I think your question is about ground motion classification, not earthquake classification, and is hence poorly phrased. Keep in mind that "engineers design for ground motions, not earthquakes" (N. Abrahamson).

Regards

Olga

thank u so much Olga

Hello,

As long as structures are concerned, and more specially critical structures such as dams and so on, 2 levels of ground motions are considered.

Level 1: Is said OBE (Operation Basis Earthquake or Design Earthquake) has usually a return period of about 475years. For design purposes, minor damages are accepted. The structure should be justified to continue fullfilling its function. Usual PGA's, depending on the seismicity of the site, could be like 0,10g - 0,20g.

Level 2: Is said SEE (SSE: Safety Evaluation Earthquake or MDE: Maximum Design Earthquake or MCE: Maximum Credible Earthquake or MCE: Maximum Considered Earthquake (such as by Atkinson). I has usually a return period of about 10,000years or more with 100,000years in some cases. It could be also evaluated based on deterministic approach without using the probabilities or the return periods. For instance, A fault that is able to delived M8 at 5km from the site will define the MCE. For design purposes, some damages damages are accepted. However, the structure should continue fullfilling its main function. For example no uncontrolled release of the reservoir in the case of dams. Usual PGA's, depending on the seismicity of the site, could be like 0,25g - 0,50g and even more. Major repair is expected after the earthquake, including partial or total progressive lowering of the reservoir using the bottom outlets or other avaible device, in the case of dams.

This is the global approach. It can be adapted for each case.

In general, for builidings, only one level, or one return period is considered. It is like 475years (10% exceedance of the PGA in 50years), but was raised in the recent past years to 2500years (2% or so exceedance of the PGA in 50years) in USA and Canada.

B. Touileb

Artelia Group///