Liquefaction Assessment: ISHIHARA
Seismic soil liquefaction assessment parameters for the Seed-Idriss simplified procedure and Boulanger-Idriss 2014 update — CRR vs (N1)60cs (SPT) and qc1N (CPT) for clean sand, magnitude scaling factors (MSF) for Mw 5.5–8.5, stress reduction coefficient rd vs depth, Kσ overburden correction, CN normalization, fines content correction delta_N, Ishihara surface manifestation H1/H2 criteria, and factor of safety thresholds.
| assessment method | parameter key | notes | parameter group | parameter name | unit | value max |
|---|---|---|---|---|---|---|
| ISHIHARA | ISHIHARA_H1_1m | H2 (critical non-liquefiable crust) ≤ 1.5 m when H1=1 m and Mw~7.5; Ishihara 1985 criterion; horizontal ground; sand volcanoes/lateral spreading can occur for H2 < H2_critical | surface_manifestation | Ishihara surface manifestation — H1=1 m | m | 1.5 |
| ISHIHARA | ISHIHARA_H1_2m | H2_critical ≈ 2.5 m when H1=2 m (liquefiable layer); no liquefaction manifestation expected for thicker crust | surface_manifestation | Ishihara surface manifestation — H1=2 m | m | 2.5 |
| ISHIHARA | ISHIHARA_H1_3m | H2_critical ≈ 3.5 m when H1=3 m | surface_manifestation | Ishihara surface manifestation — H1=3 m | m | 3.5 |
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