4　Preliminary Feasibility Study

4.1　General Requirements

4.1.1　In the preliminary feasibility study phase，investigation and evaluation shall be conducted for two or more candidate sites.

4.1.2　For the suitability of candidate sites in geological and seismic aspects，preliminary evaluation shall be performed on the basis of data collection and analysis，supported by necessary field investigation and exploration.

4.1.3　The seismic investigation and evaluation shall meet the following requirements:

1　The region evaluation shall mainly include collecting regional geological，seismic and geophysical data for a preliminary evaluation of the seismic activity and seismotectonic characteristics of the region.When existing information cannot meet the evaluation requirements in this phase，necessary investigation shall be conducted.

2　For the near region evaluation，necessary field investigation should be conducted on the basis of collecting and analyzing the existing geological，seismic and geophysical data，satellite remote sensing and（or）aerial image data，to identify the activity of main faults and preliminarily assess the seismogenic structure in the near region.

3　In the site vicinity evaluation，preliminary evaluation on whether there is any capable fault in the site vicinity shall be made on the basis of collecting relevant geological information and in conjunction with the engineering geological survey result of the site area in the phase，supported by appropriate field investigation.

4　Preliminary evaluation should be made on earthquake-induced geological disasters of the site in conjunction with the engineering geological survey data in the present phase.Relevant data shall be collected to make preliminary evaluation of induced earthquake，tsunami and lake surge.

5　Estimation of the upper value of the SL-2 ground motion peak acceleration of the site，to present the ground motion peak acceleration of the site and the basic seismic intensity with 10% probability of exceedance in 50 years.

6　Evaluation of regional crustal stability of the site area.

4.1.4　The activity of faults in near region and water area near the site shall be analyzed and judged on the basis of existing information，and for critical fracture structure that may affect the site qualification，necessary geophysical exploration shall be conducted.

4.1.5　When there is volcanic activity that may affect the site qualification in the region，investigation shall be conducted and its effect on the site shall be preliminarily assessed.

4.1.6　Subverting factors shall be basically excluded for suitable sites that are identified after evaluation，and it is permissible to handle uncertain seismic and geological issues conservatively in the depth of investigation in the current phase.