The groundwater table (GWT) depth at the CPT location is approximately 2.5 m. It may be assumed that the GWT is relatively constant (i.e., 2.5 m is the GWT depth both at the time of testing and during any earthquake being considered). Using the CLIQ program available on canvas, compute and report the Liquefaction Potential Index (LPI) for each of the three cases described below using the Boulanger and Idriss (2014) liquefaction triggering model to compute FSliq versus depth. Note that the CPT depth has units of meters and that the qc, fs, and u2 data has units of kPa. When reading in the data, you must click all four boxes on the Units Conversion tab and indicate the units for depth, qc, fs, and u2. To do so you will need to click the dropdown menus for qc, fs, and u2 and select kPa (the default is MPa). Based on historical data collection and calibration, LPI = 5 is commonly used as a classification threshold to predict whether some manifestation of liquefaction is expected at the ground surface (i.e., no manifestation is expected when LPI < 5, while some manifestation is expected when LPI > 5). Similarly, the severity of manifestation is expected to increase with increasing LPI. For example, LPI = 15 is commonly used as a classification threshold to predict severe manifestations of liquefaction, which would very likely be damaging for all civil infrastructure.

(a) Compute LPI for the 2001 M6.8 Nisqually, Washington, earthquake. Recorded peak ground accelerations in SODO were approximately 0.27 g. Does the LPI prediction generally agree or disagree with what was observed in SODO?

(b) Compute LPI for a M9 Cascadia Subduction Zone megathrust earthquake. Recent simulations by the USGS predict peak ground accelerations of 0.17 g in SODO. Assuming that LPI is an efficient predictor, would the severity of liquefaction manifestations be lesser, greater, or about the same relative to what was observed in the Nisqually event?

(c) Compute LPI for a M7.2 earthquake on the Seattle Fault, which runs east/west across SODO (see below). Recent simulations by the USGS predict peak ground accelerations of 0.60 g in SODO. Assuming that LPI is an efficient predictor, would the severity of liquefaction manifestations be lesser, greater, or about the same relative to what was observed in the Nisqually event?