THREE-AXIS BROADBAND SEISMOMETERS WITH XYZ AND UVW SENSOR CONFIGURATIONS

Abstract

Seismometers measure ground movements in three mutually perpendicular directions, one in a vertical and two in a horizontal direction, which are consistent with the cardinal directions (east-west, north-south) by international agreement. We can therefore expect that in modern broadband three-axial seismometers, all three sensors are also placed in the same way. This type of sensor arrangement is called an XYZ configuration. However, at the beginning of the 1990s a seismometer appeared on the market with a new sensor concept, where three of the rectangular sensors were arranged to form a 54.74° angle with the vertical (a UVW configuration or “cube-corner” sensor arrangement). This was the well-known STS-2 seismometer from the Swiss company Streckeisen. Today, more than 25 years later, seismometers with both concepts share the market almost equally, and both have their advantages and disadvantages, which are described in this article. In the Slovenian national seismic network, we use both types of seismometer.