Earthquakes classification

Lahr JC, Chouet BA, Stephens CD, Power JA, Page RA (1994) Earthquake classification, location, and error analysis in a volcanic environment implications for the magmatic system of the 1989-1990 eruptions at redoubt volcano, Alaska. J Volcanol Geotherm Res 62( 1 ) 137-151. doi 10.1016/0377-0273(94)90031-0... 

A general agreement exists that classification of systems, structures and components of a plant from the point of view of safety and from the point of view of resistance to external actions (earthquake, and so on) is necessary to make decisions on the following ... 

Classification for the resistance to earthquakes, with reference to the need that the component continue to be undamaged or functional during and after an earthquake of a certain severity, taking into account the aftershocks and therefore the possible incremental damage. 

Considering the possible earthquake intensity, CEFR site is localed in the region of 7 degree, near 8 degree in standard 12 degree classification, the horizontal acceleration for safe operation SI will be 0.107 g on die base rock and for safe shutdown S2 will be 0.214 g. The analysed results to die both axial and peripheric stresses of the reactor vessel (main sodium tank) under these two circumstances that the maximum of peripheric stress at bottom supported is only half of that of top supported, and also we understand the bottom supported has been well realized in BN>600. These are the main reasons to make diis change. 

The epicentre of an earthquake is located on the surface of the Earth immediately above the focus (i.e. the location of the origin of the earthquake), and shock waves radiate from the focus in all directions. Earthquake foci are confined to within a limited zone of the upper Earth, the lower boundary occurring at around 700 km depth from the surface. No earthquakes are known to have originated below this level. Moreover, earthquakes rarely originate at the Earth s surface. In fact, most earthquakes originate within the upper 25 km of the Earth. Because of its significance, the depth of foci has been used as the basis of a threefold classification of earthquakes those occurring within the upper 70 km are referred to as shallow, those located between 70 and 300 km as intermediate, and those between 300 and 700 km as deep. Seventy percent of all earthquakes are of shallow type. 

Classification for resistance to earthquakes, on the basis of the need for the structure or component considered to retain its integrity and to perform its function during and after an earthquake, taking into account aftershocks and consequent incremental damage ... 

Seismic categorization is the process by which a plant item is assigned to a seismic category in accordance with its required performance during and after an earthquake, in addition to other classifications such as safety, quaUty assurance and maintenance classifications. The relevant acceptance criterion associated with the item is part of the categorization. 

For equipment, a systematic evaluation of the possible modes of failure related to earthquakes should be carried out with reference to the acceptance criteria assigned by the safety classification. This should be carried out by means of specific tests. However, as sophisticated techniques of analysis by computer simulation are improving, even the performance of active equipment (e.g. pumps, valves and diesel generator sets) under earthquake conditions may be predicted with some confidence by means of analysis. The operability of active components may be qualified by analysis only when their potential failure modes can be identified and described in terms of stress, deformation (including clearances) or loads. Otherwise, testing or earthquake experience should be used for the qualification of active components. 

With respect to this issue, design of reactor facilities are classified in terms of seismic importance from the standpoint of radiation effects on the environment which may occur as a result of earthquake, and facilities are seismically designed in accordance with such classification. 

Influence of the local soil conditions. Miranda (1993) and Miranda and Bertero (1994) considered a wide dataset of ground motion excitations which had been previously classified according to the relevant earthquake parameters (magnitude, distance from the fault) and the local soil conditions prevalent at the site. Statistical equations of in terms of the local soil conditions were subsequently obtained, proposing the following q -ix-T evaluation function for different soil classifications (Eq. 8) ... 

Earthquake damage mapping Object-oriented classification Very high-resolution SAR and optical images... 

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