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Jäckel, K. H.
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Jäckel, K. H.
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- PublicationOpen AccessEmpirical H/V spectral ratios estimated in two deep sedimentary basins using microseisms recorded by short-period seismometers(2009-01-01)
; ; ; ; ; ;Bindi, D.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Milano-Pavia, Milano, Italia ;Marzorati, S.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Milano-Pavia, Milano, Italia ;Parolai, S.; GFZ-Potsdam ;Strollo, A.; GFZ-Potsdam ;Jäckel, K.-H.; GFZ-Potsdam; ; ; ; In this work, we analyse continuous measurements of microseisms to assess the reliability of the fundamental resonance frequency estimated by means of the horizontal-to-vertical (H/V) spectral ratio within the 0.1–1 Hz frequency range, using short-period sensors (natural period of 1 s). We apply the H/V technique to recordings of stations installed in two alluvial basins with different sedimentary cover thicknesses—the Lower Rhine Embayment (Germany) and the Gubbio Plain (Central Italy). The spectral ratios are estimated over the time–frequency domain, and we discuss the reliability of the results considering both the variability of the microseism activity and the amplitude of the instrumental noise. We show that microseisms measured by short period sensors allow the retrieval of fundamental resonance frequencies greater than about 0.1–0.2 Hz, with this lower frequency bound depending on the relative amplitude of themicroseism signal and the self-noise of the instruments. In particular,we show an examplewhere the considered short-period sensor is connected to instruments characterized by an instrumental noise level which allows detecting only fundamental frequencies greater than about 0.4 Hz. Since the frequency at which the peak of the H/V spectral ratio is biased depends upon the seismic signal-to-instrument noise ratio, the power spectral amplitude of instrumental self-noise should be always considered when interpreting the frequency of the peak as the fundamental resonance frequency of the investigated site.183 306 - PublicationRestrictedSuitability of short-period sensors for retrieving reliable H/V peaks for frequencies less than 1 Hz(2008-04)
; ; ; ; ; ;Strollo, A.; GFZ-Potsdam, Germany ;Parolai, S.; GFZ-Potsdam, Germany ;Jäckel, K.-H.; GFZ-Potsdam, Germany ;Marzorati, S.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Milano-Pavia, Milano, Italia ;Bindi, D.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Milano-Pavia, Milano, Italia; ; ; ; Using three different short-period electromagnetic sensors with resonant frequencies of 1 Hz (Mark L4C-3D), 2 Hz (Mark L-22D), and 4.5 Hz (I/O SM-6), coupled with three digital acquisition system, the PDAS Teledyne Geotech, the REFTEK 72A, and the Earth Data Logger PR6-24 (EDL), the effect of the seismic instruments on the horizontal-to-vertical spectral ratio (H/V) using seismic noise for frequencies less than 1 Hz has been evaluated. For all possible sensors - acquisition system pairs, the background seismic signal and instrumental self-noise power spectral densities have been calculated and compared. The results obtained when coupling the short-period sensors with different acquisition systems show that the performance of the considered instruments at frequencies < 1 Hz strongly depends upon the sensor-acquisition system combination and the gain used, with the best performance obtained for sensors with the lowest resonance frequency. For all acquisition systems, it was possible to retrieve correctly the H/V peak down to 0.1-0.2 Hz by using a high gain and a 1 Hz sensor. In contrast, biased H/V spectral ratios were retrieved when low-gain values were considered. Particular care is required when using 4.5 Hz sensors since they may not even allow the fundamental resonance frequency peak to be reproduced133 24 - PublicationRestrictedOn the suitability of 1 s geophone for ambient noise measurements in the 0.1–20Hz frequency range: experimental outcomes(2008-02)
; ; ; ; ;Strollo, A.; GFZ, Potsdam, Telegrafenberg, 14473 Potsdam, Germany ;Bindi, D.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Milano-Pavia, Milano, Italia ;Parolai, S.; GFZ, Potsdam, Telegrafenberg, 14473 Potsdam, Germany ;Jäckel, K. H.; GIPP Geophysical Instrumental Pool Potsdam, Potsdam, Germany; ; ; Following the ongoing debate about suitability of short-period sensor for seismic noise measurements at frequencies lower than 1Hz, in this study we compare recordings from two different seismometers (Güralp CMG-3ESPC and Mark L4C-3D) installed side by side in the GeoForschungsZentrum laboratory. The comparison carried out in terms of Power Spectral Density and coherency analysis shows an excellent agreement between the shortperiod and the broad-band recordings in the frequency band 0.2–20 Hz. Therefore, this result highlights that with a calibrated short-period sensor one can obtain the same results that would be obtained by using a broad-band seismometer in the band of engineering interest.125 22