# Six-degree-of-freedom near-source seismic motions II: examples of real seismogram analysis and S-wave velocity retrieval

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## Abstract

Near-source records obtained by the mechanical seismic sensor Rotaphone are presented. The Rotaphone can measure six components of seismic movements, three translational and three rotational. The apparent S-wave phase velocity is determined and the possibility to obtain the wavepath S-wave velocity directly under the receiver is discussed. Rotation-to-translation ratios (RTRs) characterize the strength of rotations compared to translations. The Rotaphone records of local microearthquakes were obtained in various European seismoactive regions over the last few years. Three case studies, analyzed in detail, include various geological structures and seismograms recorded at various epicentral distances from 0.7 to 14.9 km. Also, the source depth varies from 4.8 to 10.4 km. The first case is an event from the West Bohemia intraplate seismic swarm region. The seismogram was recorded only 0.7 km from the epicenter. This case shows the complexity of rotation-to-translational relations near the epicenter. The second case is from the Corinthian Gulf active-rift region. The study confirms the expectation of the theory concerning rotations connected with the direct S wave; however, difficulties follow from a very complex 3D geological structure in the vicinity of the station, complicated by a distinctive topography with steep slopes of the hills. The third example is from South Iceland, near the active Katla volcano. The data in this case satisfy the rotation-to-translation relations very well, which is probably caused by the relatively simple geological setting and appropriate source-to-receiver configuration. The RTRs are computed for all three cases, and their frequency dependence is discussed.

## Keywords

Seismic rotation Near-source region Rotational seismometer Microearthquakes West Bohemia/Vogtland region Gulf of Corinth Katla region## Notes

### Acknowledgements

This work was supported by the Czech Science Foundation, Projects No. P210/10/0925, P210/12/ 2336, and P210/15-02363S. Measurements at the WEBNET station NKC, West Bohemia, were supported by the CzechGeo/EPOS project. Measurements in Greece were performed in the framework of the bilateral cooperation between the Charles University in Prague and the University of Patras. We are grateful to Bergur H. Bergson, Icelandic Met Office, for technical help with installing the Rotaphone at the ESK station. Topographic data were obtained from ASTER GDEM, a product of NASA and METI.

## References

- Abercombie RE, Main IC, Douglas A, Burton PW (1995) The nucleation and rupture process of the 1981 Gulf of Corinth earthquakes from deconvolved broad-band data. Geophys J Int 120:393–405CrossRefGoogle Scholar
- Belfi J, Beverini N, Bosi F, Carelli G, Di Virgilio A, Kolker D, Maccioni E, Ortolan A, Passaquieti R, Stefani F (2012) Performance of “G-Pisa” ring laser gyro at the Virgo site. J Seismol 16(4):757–766CrossRefGoogle Scholar
- Bouchon M, Aki K (1982) Strain, tilt, and rotation associated with strong ground motion in the vicinity of earthquake faults. Bull Seismol Soc Amer 72(6):1717–1738Google Scholar
- Brokešová J, Málek J (2010) New portable sensor system for rotational seismic motion measurements. Rev Sci Instrum 81:084501. doi: 10.1063/1.3463271 CrossRefGoogle Scholar
- Brokešová J, Málek J, Kolínský P (2012a) Rotaphone, a mechanical seismic sensor system for field rotation rate measurements and its in situ calibration. J Seismol 16(4):603–622. doi: 10.1007/s10950-012-9274-y CrossRefGoogle Scholar
- Brokešová J, Málek J, Evans JR (2012b) Rotaphone, a new self-calibrated six-degree-of-freedom seismic sensor. Rev Sci Instrum 83:086108. doi: 10.1063/1.4747713 CrossRefGoogle Scholar
- Brokešová J, Málek J (2013) Rotaphone, a self-calibrated six-degree-of-freedom seismic sensor and its strong-motion records. Seismol Res Let 84(5):737–744. doi: 10.1785/0220120189 CrossRefGoogle Scholar
- Brokešová J, Málek J (2014) Six-degree-of-freedom near-source seismic motions I: rotation-to-translation relations and synthetic examples. J Seismol. (this issue)Google Scholar
- Brož M, Ŝtrunc J (2011) A new generation of multichannel seismic apparatus and its practical application in standalone and array monitoring. Acta Geodyn Geomater 8(3):345–352Google Scholar
- Cochard A, Igel H, Schuberth B, Suryanto W, Velikoseltsev A, Schreiber U, Wassermann J, Scherbaum F, Vollmer D (2006) Rotational motions in seismology: theory, observations, simulation. In: Teisseyre R, Takeo M, Majewski E (eds) Earthquake source asymmetry, structural media and rotation effects. Springer-Verlag, Berlin Heidelberg, pp 391–412CrossRefGoogle Scholar
- Fichtner A, Igel H (2009) Sensitivity densities for rotational ground motion measurements. Bull Seismol Soc Amer 99:1302–1314CrossRefGoogle Scholar
- Igel H, Cochard A, Wassermann J, Flaws A, Schreiber U, Velikoseltsev A, Pham ND (2007) Broad-band observations of earthquake-induced rotational ground motions. Geophys J Int 168:182–196CrossRefGoogle Scholar
- Igel H, Brokešová J, Evans JR, Zembaty Z (2012) Preface to the special issue on advances in rotational seismology: instrumentation, theory, observations, and engineering. J Seismol 16:571–572. doi: 10.1007/s10950-012-9307-6 CrossRefGoogle Scholar
- Jakobsdóttir SS (2008) Seismicity in Iceland: 1994–2007. Jökull 58:75–100Google Scholar
- Jaroszewicz LR, Krajewski Z, Kowalski H, Mazur G, Zinówko P, Kowalski J (2011) AFORS autonomous fibre-optic rotational seismograph: design abd application. Acta Geophys 59(3):578–596CrossRefGoogle Scholar
- Jedlička P, Kozák JT, Evans JR, Hutt CR (2012) Designs and test results for three new rotational sensors. J Seismol 16(4):639–648CrossRefGoogle Scholar
- Knejzlík J, Kaláb Z, Rambouský Z (2012) Adaptation of the S-5-S pendulum seismometer for measurement of rotational ground motion. J Seismol 16(4):649–656CrossRefGoogle Scholar
- Knopoff L, Chen YT (2009) Single-couple component of far-field radiation from dynamical fractures. Bull Seismol Soc Amer 99(2B):1091–1102CrossRefGoogle Scholar
- Kolínský P, Brokešová J (2007) The Western Bohemia uppermost crust shear wave velocities from Love wave dispersion. J Seismol 11(1):101–120CrossRefGoogle Scholar
- Lee WHK, Huang B-S, Langston CA, Lin C-J, Liu C-C, Shin T-C, Teng T-L, Wu C-F (2009) Review: progress in rotational ground-motion observations from explosions and local earthquakes in Taiwan. Bull Seismol Soc Amer 99:958–967CrossRefGoogle Scholar
- Málek J, Horálek J, Janský J (2005) One-dimensional qP-wave velocity model of the upper crust for the West Bohemia/Vogtland earthquake swarm region. Stud Geophys Geod 49:501–524. doi: 10.1007/s11200-005-0024-2 CrossRefGoogle Scholar
- Moriya T, Teisseyre R (2006) Design of rotation seismometer and non-linear behaviour of rotation components of earthquakes. In: Teisseyre R, Takeo M, Majewski E (eds) Earthquake source asymmetry, structural media and rotation effects. Springer-Verlag, Berlin Heidelberg, pp 439–450CrossRefGoogle Scholar
- Nigbor RL, Evans JR, Hutt CR (2009) Laboratory and field testing of commercial rotational seismometers. Bull Seismol Soc Amer 99:1215–1227CrossRefGoogle Scholar
- Pujol J (2009) Tutorial on rotations in the theories of finite deformation and micropolar (Cosserat) elasticity. Bull Seismol Soc Amer 99(2B):1011–1027CrossRefGoogle Scholar
- Schreiber U, Klügel T, Stedman GE (2003) Earth tide and tilt detection by a ring laser gyroscope. J Geophys Res 108(B2):2132. doi: 10.1029/2001JB000569 CrossRefGoogle Scholar
- Schreiber U, Hautmann JN, Velikoseltsev A, Wassermann J, Igel H, Otero J, Vernon F, Wells JPR (2009) Ring laser measurements of ground rotations for seismology. Bull Seismol Soc Amer 99:1190–1198CrossRefGoogle Scholar
- Stedman GE (1997) Ring laser tests of fundamental physics and geophysics. Rep Progr Phys 60:615–688CrossRefGoogle Scholar
- Stejskal V, Málek J, Novotný O (2008) Variations in discharge and temperature of mineral springs at the Františkovy lázně spa, Czech Republic, during a nearby earthquake swarm in 1985/1986. Stud Geophys Geod 52:589–606CrossRefGoogle Scholar
- Suryanto W, Igel H, Wassermann J, Cochard A, Schuberth B, Vollmer D, Scherbaum F, Schreiber U, Velikoseltsev A (2006) First comparison of array-derived rotational ground motions with direct ring laser measurements. Bull Seismol Soc Amer 96(6):2059–2071CrossRefGoogle Scholar
- Takeo M (1998) Ground rotational motions recorded in near-source region of earthquakes. Geophys Res Let 25(6):789–792CrossRefGoogle Scholar
- Velikoseltsev A, Schreiber KU, Yankovsky A, Wells J-PR, Boronachin A, Tkachenko A (2012) On th application of fiber optic gyroscopes for detection of seismic rotations. J Seismol 16(4):623–637. doi: 10.1007/s10950-012-9282-y CrossRefGoogle Scholar
- Willis CJ, Petersen M, Bryant WA, Reichle M, Saucedo GJ, Tan S, Taylor G, Treiman J (2000) A site-conditions map for California based on geology and shear-wave velocity. Bull Seismol Soc Amer 90(6B):S187–S208CrossRefGoogle Scholar