### 2.197 Margaris et al. (2002b) & Margaris et al. (2002a)

• Ground-motion model is:

where Y is in cms2, c0 = 4.16, c1 = 0.69, c2 = -1.24, R0 = 6, c3 = 0.12 and σ = 0.70.

• Use three site categories:
S = 0
NEHRP and UBC category B. 145 records.
S = 1
NEHRP and UBC category C. 378 records.
S = 2
NEHRP and UBC category D. 221 records.
• Selection criteria are: a) earthquake has Mw 4.5, b) PGA 0.05g and c) PGA < 0.05g but another record from same earthquake has PGA 0.05g.
• Records mainly from normal faulting earthquakes.
• Exclude data recorded in buildings with four stories or higher.
• Automatically digitize records and process records homogenously, paying special attention to the filters used.
• Correlation between Mw and R in set of records used. For 4.5 Mw 5.0 records exist at R 40km and for larger magnitudes records exist at intermediate and long distances. For Mw > 6.0 there is a lack of records for R < 20km.
• Use a two step regression method. In first step use all records to find c1. In second step use records from earthquakes with Mw 5.0 to find c0, c2 and c3.
• Adopt R0 = 6km because difficult to find R0 via regression due to its strong correlation with c2. This corresponds to average focal depth of earthquakes used.
• Also try Ground-motion model: lnY = c0+c1Mw+c2 ln(R2+h02)12+c3S. Coefficients are: c0 = 3.52, c1 = 0.70, c2 = -1.14, h0 = 7km (adopted), c3 = 0.12 and σ = 0.70.
• Find no apparent trends in residuals w.r.t. distance.
• Due to distribution of data, equations valid for 5 R 120km and 4.5 Mw 7.0.