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Analysis of a group of seismic events using rotational components

Teisseyre K.P.

Acta Geophysica

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2007

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Vol. 55, no. 4

535-553

EN

Analysis of a group of seismic events which took place in central Italy and have been recorded at the l’Aquila Observatory reveals proportionality between the maximum seismic signal (the displacement velocity) and the maximum amplitudes of rotational components. To compare the seismic events in the aspect of energy emitted as rotational motions, the rotation indices are used; these indices help us also to differentiate between the results obtained for different frequency spectra. In the adopted higher frequency range, 2.6-43 Hz, the relation between maximum displacement velocities and the rotation indices is roughly reciprocal, while for the lower frequencies, 0.3-3 Hz, there is no clear relationship. The share of rotation motions in the whole seismic energy emitted from the source varies during the seismic event. Research on the rotational components hidden in the seismic field gives a new insight into the processes in the source.

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Seismic events and rotation waves in the Hans Glacier, Spitsbergen, and the Pasterze Glacier, Austria

Teisseyre K., Górski M., Suchcicki J.

Acta Geophysica Polonica

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2004

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Vol. 52, nr 4

465-476

EN

Methods of recording and data analysis that jointly allow to estimate rotation components in the seismic field were applied at two glaciers: the Hans Glacier in the Spitsbergen archipelago behind the North Polar Circle and the Pasterze Glacier in the Austrian Alps. A substantial content of rotation velocity components was found in the data collected at both locations; especially high rotation amplitudes were found in the Hans Glacier. Differences between the results obtained from these two glaciers are shown and briefly discussed.

3

Seismic rotation waves related to volcanic, mining and seismic events: Near-field and micromorphic motions

Teisseyre R., Teisseyre K., Moriya T., Palangio P.

Acta Geophysica Polonica

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2003

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Vol. 51, nr 4

409-431

EN

Rotation and twist waves recorded in Hokkaido (Japan), Ojców and Książ (Poland) and L'Aquila (Italy) bring a new insinght into the features of these motions for volcanic, mining and tectonic events. The rotation seismograph system used at the observatories in Hokkaido differs from that observatories in Poland and Italy. Nevertheless, the results obtained, for all observatories, are compatible. The levels of rotation and twist motions depend distinctly on the back-ground properties of the recording sited. Moreover, at a given recording station we have noticed two different levels of these motions; for some near events the records indicate very small rotation motions, while for other, also near events, these motions are distinctly greater and remain on a similar level as those for records from the distant sources. For the near events the evident differences in magnitudes and character of these motions suggest a distinct relation between the rotation and twist motions and the source mechanism. Similarly, an analysis of records for the volcanic events indicates existence of two kinds of events: for the first group, the rotation components reach the order of magnitude much greater than those for the group, for which the rotation and twist motions are quite negligible. The records related to this group, representing probably the near-surface volcanic explosions, confirm at the same time the reliability of results obtained for the rotation motions belonging to the first group, as the technique of recording and distances remain for both groups the same. The records from several stations give grounds for searching for as influence local structure on rotation and twist motions. The data treatment applied for local events made it possible to separate the recorded motions into the micromorphic and source related parts.

4

Application of Fiber-Optic Sagnac Interferometer for Detection of Rotational Seismic Events

Jaroszewicz L., Krajewski Z., Świłło R.

Molecular and Quantum Acoustics

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2001

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Vol. 22

133-144

EN

A new area of fiber-optic Sagnac interferometer application is presented and discussed. The fiber-optic sensor described in the paperm in well-known classic FOG configuration, has been designed for a detection of the rotational seismic events. The basic system optimisation for a detection rotation only without cenversion for rotation ac give an advantage for this system in compare to other rotational seismometers, which calculate rotational events in indirect ways. The comparison of data from th described fiber-optic rotation seismometer and two antiparallel pendulum seismometers are also presented.