An Important Update for the Engineering Geological Database for TSMIP

An Important Update for the Engineering Geological Database for TSMIP

The Engineering Geological Database for TSMIP was published several years ago. This database provides data regarding geological logging and velocities at 439 free-field strong motion stations throughout Taiwan. Precise Vs30 values were calculated using the measurements of the suspension PS-logging method at those stations, and therefore an essential site parameter is available for strong motion prediction equations, seismic hazard assessments, and the national seismic design code. However, there are more than 700 strong-motion stations in Taiwan. When site parameters become available for more strong motion stations, related studies will benefit from the site database. Therefore, although the investigation was closed in 2012, we continue the observation of velocity profiles. Velocity profiles at eighteen stations were added into the database, as well as the measured Vs30s. We assess the accuracy of the estimated Vs30s, which have been published in other studies using different proxy-based approaches; we also refer to the Vs30 selection criterion proposed by the NGA project. The estimated Vs30s from previous studies are then selected for stations without logging data in our database in order to complement the required site parameters for comprehensive usage of strong motion recordings in Taiwan. The updated site database currently contains Vs30 values at more than 800 stations for further studies. Moreover, another site parameter from recent studies, Z1.0, the depth of the velocity horizon with an S-wave velocity of more than 1.0 km/s, has been included in this database. The upgraded EGDT is used for national seismic hazard analyses.