- Ground-motion model is:
- Response parameter is pseudo-velocity for 5% damping.
- Use R1, distance from hypocentre to volcanic front, and R2, distance from volcanic front to site, to model
- Use data from K-Net. Select earthquakes that: 1) have Mw > 5 and 2) have more than 50 available records.
To remove bias due to large number of records from fore-arc site compared to back-arc, select only those
earthquakes with 40% of the available records within 300km are from back-arc region. Use both interplate
and intraslab events occurring in fore-arc region so that effect of low Q zone is clearly seen. Only use
records up to 300km so that peaks are due to S-wave motions. Exclude records from Mw8 earthquakes
because these events radiate strong surface waves so assumption of S-wave peaks may not be valid.
- Focal depths, D, of intraslab earthquakes between 59 and 126km and for interface
earthquakes between 21 and 51km.
- Also derive model using: log 10Y (T) = c + aMw + hD - log 10R - bR. Find lower σs for functional form
using R1 and R2 for periods < 1s. Examine residuals w.r.t. rhypo for 0.1 and 1.0s with grey scale indicating
ratio R1∕(R1 + R2) for this functional form. Note that fore-arc sites have positive residuals and back-arc
sites negative residuals. Also plot residuals for selected functional form and find that residuals do not show
difference between fore-arc and back-arc sites.
- Regress separately for intraslab and interface earthquakes because source characteristics significantly
- Find that the coefficients for anelastic attenuation for fore-arc and back-arc different for periods < 2s.
- Convert computed anelastic coefficients to Q models and find that can relate observations to different Q
models for fore-arc and back-arc regions.