Performance Test of a Commercial Rotational Motions Sensor

Abstract

Abstract The application of rotational motion sensors has only recently proven to give new ways of measuring seismic-wave-field properties when comparing the recorded data with seismograms of collocated traditional seismometers. The data in these test cases were produced using either sophisticated and thus expensive ring laser technology or cumbersome seismic array techniques including some restrictive assumption about the wave field. In this article, we want to test the performance of one of the first medium-priced commercial rotational motion sensor (eentec R 1) by comparing its output with the aforementioned classical array-derived rotational motions. The data set consists of seismic array and rotational motion measurements that were performed during a demolition blast of a 50 m high building in the city of Munich (Germany). In addition to the simple comparison of the outputs, we want to classify the performance of the two methods by comparing derived wave-field properties with the result of classical frequency-wavenumber ( f - k ) array analysis. The results of this experiment demonstrate that, when using an array technique for estimating rotational motions, much effort in site selection, array design, and a priori knowledge of subsurface conditions is needed. It also becomes evident that the performance of an array and its estimated quantities strongly depends on the number of deployed seismic stations. Given the uncertainties in both the array-derived measurements and the rotation sensor transfer function, it is difficult to quantify the accuracy of the rotation sensor data, which indicates the need for further extensive laboratory and field testing.