過去的地震危害度分析所選用的傳統地動預估式(Ground-Motion Prediction Equation, GMPE)是採用大區域內多個測站記錄到多個不同地震源的地動紀錄所建立的，因此包含過多的地動值變異性，會造成危害度過估。本研究提出一新方法來建立場址相依地動預估式(site-dependent GMPE)，期能降低地動預估式中的地動值不確定性，以避免在機率式地震危害度分析中做成過度保守的估計。本研究以牡丹水庫場址為例，篩選距離工址70公里範圍內且與工址有相似場址特性的測站所收錄之地動記錄來建立該地區地殼地震的場址相依地動預估式，其與台灣現有的區域地動預估式相比，地動值標準差明顯降低許多。本研究也以場址相依地動預估式建立均佈度危害反應譜，其結果與以區域地動預估計算的結果相比，有大幅下降的情形。 透過場址相依地動預估式來進行分析，雖可降低場址效應，然而地震波的衰減還受震源特性及波傳遞路徑影響，故在震源參數上，本研究進一步將震源分區加入地動預估式，建立小震源區對小場址範圍的地動預估式，又稱場址相依暨小震源分區地動預估式(site-dependent with small source zone GMPE)，其與場址相依地動預估式相比下，地動值變異性標準差再降低約10%，而均佈危害度反應譜也因此下修。 本研究再進一步進行單一測站的地動預估式與小震源區對單一測站的地動預估式研究，建立場址特定地動預估式(site-specific GMPE)與場址特定暨小震源分區地動預估式(site-specific with small source zone GMPE)，探討更接近理想中的單一路徑地動預估式。然而在資料量的限制與地動預估式的穩健特性權衡下，本研究初步得知場址相依或場址相依暨小震源分區地動預估式具可行性，可以為重要基礎設施的設計或安全評估提供更準確、更合理的地動值預估。 ;Traditional ground-motion prediction equations (GMPEs) are based on datasets of ground-motion parameters recorded at multiple stations and different earthquakes in various source regions. It causes excessive ground-motion variability and leads to increasing seismic hazard estimations. This study proposes a new method to establish a site-dependent GMPE, which reduces the uncertainty of ground-motion value in the GMPE and avoids over-conservative estimation in probabilistic seismic hazard analysis (PSHA). Take the Mudan Reservoir site as an example, this study selected ground-motion records with similar site conditions from the stations within 70 km of the studied site to build a site-dependent ground-motion prediction model for crustal earthquakes in this region. This site-dependent GMPE set obtains a significantly smaller standard deviation compared with the existing regional GMPEs from the Taiwan data set. This study also builds a uniform hazard response spectrum with a site-dependent GMPE, and the result is sharply decreased compared with that with the regional GMPE. Although analyzing through the site-dependent GMPEs can reduce the site effect, the attenuation of seismic waves is also affected by source characteristics and wave propagation paths. Therefore, this study further added seismic source zones to the GMPE and established a small source zone to small site area model, which is also known as site-dependent with small source zone GMPE. The standard deviation of this GMPE is reduced by about 10% compared with site-dependent one, and the uniform hazard response spectrum is also decreased. In this study, we also conducted a research on site-specific GMPEs and site-specific with small source zone GMPEs to discuss more ideal single-path GMPEs. However, under the limitation of data numbers and the robustness of GMPEs, we only got a preliminary result that indicates the site-dependent GMPEs or site-dependent with small source zone GMPEs are feasible, and they can provide a more accurate and reasonable prediction of ground-motion levels for the design or safety evaluation of important infrastructures.
