- journal_title：Bulletin of the Seismological Society of America
- Contributor：Hsi-Ping Liu ; Robert L. Maier ; Richard E. Warrick
- Publisher：Seismological Society of America
- Date：1996-
- Format：text/html
- Language：en
- journal_abbrev：Bulletin of the Seismological Society of America
- issn：0037-1106
- volume：86
- issue：2
- firstpage：530
- section：Short Notes
We have previously constructed an air-powered, impulsive, <em>SHem>-wave source for shear-wave velocity measurements using a downhole configuration. One shortcoming of that source is the existence of a forerunning signal generated by the reaction to the rapid acceleration of an inertial mass when a poppet value is opened. By changing the poppet valve to a ball valve, a cleaner signal is generated. The improvement comes about because when a ball valve is opened, its flow capacity increases gradually, resulting in a smooth and gradual acceleration of the inertial mass. Tests involving ground coupling and driving air pressure were conducted to investigate physical parameters of shear-wave generation. We illustrate as an application the measurement of shear-wave velocity in a loess layer.