摘要：This paper analyzes the seismicity in bohai sea,introducing a shape factor K to characterize the seismic risk distribution in sub-regions of the sea. Based on the seismic design ground motions for 46 platforms located in the bohai sea,a statistical analysis was performed for different peak ground acceleration (PGA) ratios at two different probability levels. In accordance with the two-stage design method,a scheme of two seismic design levels is proposed,and two seismic design objectives are established respectively for the strength level earthquake and the ductility level earthquake. By analogy with and comparison to the Chinese seismic design code for buildings,it is proposed that the probability level for the strength level earthquake and ductility level earthquake have a return period of 200 and 1000 - 2500 years,respectively. The validity of these proposed values is discussed. Finally,the PGAs corresponding to these two probability levels are calculated for different sub-regions of the bohai sea.

摘要：The bohai sea is one of the southernmost areas for sea ice formation in the northern *** ice disasters in this body of water severely affect marine activities and the safety of coastal *** this study,we analyze the variation characteristics of the sea ice in the bohai sea and establish an annual regression model based on predictable mode analysis *** results show the following:1)From 1970 to 2018,the average ice grade is(2.6±0.8),with a maximum of 4.5 and a minimum of *** Bay(LDB)has the heaviest ice conditions in the bohai sea,followed by bohai Bay(BHB)and Laizhou Bay(LZB).Interannual variation is obvious in all three bays,but the linear decreasing trend is significant only in BHB.2)Three modes are obtained from empirical orthogonal function analysis,namely,single polarity mode with the same sign of anomaly in all of the three bays and strong interannual variability(82.0%),the north–south dipole mode with BHB and LZB showing an opposite sign of anomalies to that in LDB and strong decadal variations(14.5%),and a linear trend mode(3.5%).Critical factors are analyzed and regression equations are established for all the principal components,and then an annual hindcast model is established by synthesizing the results of the three *** model provides an annual spatial prediction of the sea ice in the bohai sea for the first time,and meets the demand of operational sea ice forecasting.

摘要：This paper analyzes the seismicity and seismic risk distribution in the bohai sea. Based on the seismic design parameters of 46 platforms in the bohai sea, a statistic analysis is made on the ratios of the peak accelerations for different probability levels. In accordance with the two-stage design method, a scheme of two design seismic levels is proposed, and two fortification goals are established respectively for strength level earthquakes and ductility level earthquakes. Through analogy and comparison to the Chinese seismic code for buildings, it is proposed that the probability level for the strength and ductility level earthquakes takes return periods of 200a and 1000～2500a respectively, and we further expounded on its rationality. Finally, the fortification parameters in the sub-regions of bohai sea area are given in the light of seismic risk zonation and ground motion division. This article is a summary of experiences from many years of offshore platform seismic fortification work, and an exploratory study on the seismic fortification standards of offshore platforms in China, which may provide some references for the establishment of the standard.

摘要：Wave fields in bohai sea from 1985 to 2004 were simulated using SWAN wave model by inputting high-resolution hindcast wind fields dataset. Comparisons of wave heights between simulation and observation show good agreement in general. According to the annual extreme values of simulation, this paper gives wave extreme parameters with different return-period for all computation grids in bohai sea.