History of developement

Older prototypes

• 3DOF DISK measures vertical-axis rotation rate plus two perpendicular horizontal ground velocity components
• 6DOF KOSTKA measures 3 components rotation rate and 3 components ground velocity

For more details, see prototypes webpage

The prototypes are described in papers:

• Brokešová J. and J. Málek (2010). New portable sensor system for rotational seismic motion measurements, Rev. Sci. Instrum., Vol. 81, No. 8, 084501, DOI: 10.1063/1.3463271
• Brokešová J., J. Málek, and J.R. Evans (2012). Rotaphone, a new self-calibrated six-degree-of-freedom seismic sensor, Review of Scientific Instruments, Vol. 83., 086108, DOI: 10.1063/1.4747713
• Brokešová J., J. Málek, and P. Kolínský (2012). Rotaphone, a mechanical seismic sensor system for field rotation rate measurements and its in-situ calibration, J. Seismol., Vol. 16, No.4, 603–621, DOI: 10.1007/s10950-012-9274-y
• Brokešová J. and J. Málek (2013). Rotaphone, a Self-Calibrated Six-Degree-of-Freedom Seismic Sensor and Its Strong-Motion Records, Seismol. Res. Let., Vol. 84, No. 5, 737–744, DOI: 10.1785/0220120189
• Brokešová J. and J. Málek (2015). Six-degree-of-freedom near-source seismic motions II: Examples of real seismogram analysis and S-wave velocity retrieval, J. Seismol., Vol.19, No. 2, 511–539, DOI: 10.1007/s10950-015-9480-5

Laboratory testing

The instruments were successfully tested at Albuquerque Seismological Laboratory of U.S. Geological Survey (Brokešová et al., 2012). During the development of the Rotaphone, all the prototypes were repeatedly tested in laboratory conditions. In 2009–2010 the tests were carried on in the laboratories of the Faculty of Mechanical Engineering, Czech Technical University in Prague, and of the Institute of Geophysics, AS CR. At that stage the tests were focused on basic functionality of the instruments. In spring 2011, both 3DOF and 6DOF prototypes underwent thorough testing at the USGS Albuquerque Seismological Laboratory (ASL), New Mexico, USA (Brokešová et al., 2012).

Albuquerque Seismological Laboratory is oriented especially on testing various seismic sensors, the rotational not excluding. It is equipped with a high-precision computer-controlled rotational shaking table (ARMS-260- ES16780, Aerotech Inc.) which can shake along the vertical axis or the horizontal axis, and further with a horizontal shake table of Russian provenance designed to produce precise translational motions (Nigbor et al., 2009). A fiber optic gyroscope (FOG; mFORS-1 143962-1000, Northrop Grumman LITEF Ltd.) attached to the table was used as the reference sensor. The tests were focused on functionality, linearity, and cross-axis sensitivity.

Real condition testing

The instruments were tested in the field using anthropogenic source:

• generator of the seismic motion (patent CZ 301218)
• quarry blasts in quarries Hvizdalka, Klecany and Cenkov

The tests confirmed good functionality of all the prototypes. The results of tests, in combination with results of various in-field measurements mostly designed for testing purposes, have approved that the Rotaphones are fully functional instruments providing reliable collocated short-period records of both seismic translations and rotations induced by natural and/or anthropogenic sources at distances from meters up to several hundred kilometers. For more details, see Brokešová, 2015

Since 2008 we have organized a number of short-term as well as several-months-lasting measuring campaigns in various regions with totally different seismotectonic characteristics. The list involves regions in the Czech Republic (West Bohemia/Vogtland, the vicinity of Prague, the Hronov-Poříčí fault zone) and abroad (the Provadia region in Bulgaria, the Gulf of Corinth, Greece, and the volcanic complex of Eyafjalla and Katla in South Iceland). Selected results, ordered by epicentral distance, are listed in the table as examples.

Presence

A new 6DOF prototype of Rotaphone, Rotafon-D, was constructed in 2015

Figure 1: The previous prototype 6DOF-C (left) and the new prototype 6DOF-D (right)

At present we have two such instruments in our disposal, one is funded by Technology Agency of the Czech Rapublic, TACR (project GAMMA, see also grant request), the other one, identical, was purchased with the support from the Department of Geophysics, Faculty of Mathematics and Physics, Charles University in Prague. TACR supports development and testing of this prototype.

Documentation and technical parameters

see Prototype documentation