## 2 Seismic Microzoning in Thailand  
In Thailand, interest in seismic hazard studies has been limited due to the low number of such seismic events. However, recently, the number of such studies has increased due to higher awareness of seismic hazards. In this section, seismic microzoning and other seismic-related studies conducted in Thailand are reviewed. [PERSON] et al. (2006) studied the amplification of peak ground acceleration and spectral acceleration in Bangkok [10]. In the same year, [PERSON] et al. (2006) also studied seismic effects in Bangkok due to a distant earthquake [11]. [PERSON] and [PERSON] (2007) performed a study of V\({}_{\rm S30}\) based on frequency-wavenumber (f-k) spectral analyses [12]. The results from those studies were then used for seismic microzoning in the Bangkok metropolitan area. [PERSON] and [PERSON] (2011, 2012) conducted a similar study using the SPAC method for the analysis process at the same study site [13; 14]. [PERSON] et al. (2003) studied V\({}_{\rm S30}\) using the seismic cone penetration test [15]. [PERSON] (2003) also determined V\({}_{530}\) values from boreholes from the Bangkok area [16]. [PERSON] (2007) performed a comparison between the multichannel analysis of surface wave (MASW) and borehole methods for obtaining V\({}_{530}\) values in the Bangkok metropolitan area using NEHRP standards [17]. [PERSON] et al. (2009) studied V\({}_{530}\) with N values obtained from standard penetration test observations in the Chiang Mai, Chiang Rai, and Bangkok metropolitan areas [18]. [PERSON] (2010) compared 2 sSPAC and horizontal-to-vertical (_H/V_) spectral ratio observations in the Chiang Mai, Chiang Rai, and Bangkok metropolitan areas [19; 20]. The above studies examining soil characteristics produced different types of hazard maps. However, past studies did not extensively explore certain areas, particularly Chiang Rai. In this study, we conducted field surveys and used V\({}_{530}\) values from previous studies in an area with a high frequency of earthquake incidents [21]. Seismic studies in Thailand began later than in other earthquake-prone countries. As such, certain areas remain to be addressed, especially in the northern part of the country where there are many active faults. There are many past studies that observed soil characteristics to create seismic hazard maps. [PERSON] et al. (2010, 2012) applied the MASW method to acquire V\({}_{530}\) values in Bangkok in 2010, and downtown Chiang Rai in 2012. The results were based on the NEHRP classes by spatial interpolation [22; 23]. In comparison with this research, the current study covers a larger site. Therefore, data collection during the field survey was challenging. The SPAC method was selected for its convenience in terms of time, labor, and other resource consumption. Another past study that represents soil characteristics as a seismic hazard map was that by [PERSON] et al. (2003) [24]. This study used more than 150 stations to determine the _H/V_ spectral ratio observation in the Bangkok metropolitan area. The results of the natural period ranges of the sites, their effects on tall buildings, and the long natural periods of the site effects on tall infrastructure and long-span bridges were discussed. These past studies represented the soil characteristics in the form of polygon-based features from the point-based feature. The representation of soil characteristics based on some proxy is another main consideration point in the current research. [PERSON] et al. (2006) suggested the use of geomorphology maps for V\({}_{530}\) mapping [25; 26]. The results from this study were used throughout Japan for site classification and applied to the web-based quick estimation system of strong ground motion. Later, [PERSON] et al. (2002) and [PERSON] et al. (2012) also demonstrated the relationship between geomorphologic units and site amplification ratios in Japan [27; 28]. Furthermore, geomorphology was also applied in a liquefaction potential analysis and other [29; 30; 31].