UNIVERSITY OF BUCHAREST
FACULTY OF PHYSICS

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2024-11-23 18:00

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Conference: Bucharest University Faculty of Physics 2022 Meeting


Section: Atmosphere and Earth Science; Environment Protection


Title:
Seismic noise analysis in the microseismic and high-frequency domain at the Romanian seismic stations


Authors:
Tolea Andreea (1,2), Neagoe Cristian (1), Grecu Bogdan (1), Toader Victorin (1), Moldovan Iren (1)


*
Affiliation:
1) National Institute for Earth Physics, Măgurele, Romania

2) Faculty of Physics, University of Bucharest, Bucharest, Romania


E-mail
tolea.andreea@infp.ro


Keywords:
ambient seismic noise, wind speed, single and double frequency peak, seasonal variations


Abstract:
In the absence of earthquakes, seismic stations continuously record the Earth's vibrations, called ambient seismic noise (ASN). The main concern coming from the ASN records is improving the seismic data quality using different tools developed especially for this purpose. Power Spectral Densities (PSD) and their corresponding Probability Density Functions (PDF) are tools used to evaluate the station performance and show the noise level at the station’s site. For high frequencies (>1Hz), the noise sources are from cultural activities and show diurnal variation, while for low frequencies (<1Hz), the noise is generated by natural sources and shows seasonal variation. In this study, we analyzed the vertical components of the Romanian seismic stations to characterize the noise levels at the stations and investigate noise variations in space and time. We found similar features related to the single and double-frequency peaks for several stations in eastern Romania. These peaks have a natural origin and are related to oceanic waves. We examined the relationship between noise levels and weather parameters (e.g., wind speed) for the stations where seismic sensors are collocated with weather sensors. We show that an increase in wind speed leads to an increase in the noise level at high frequencies (> 2 Hz). Also, we computed four-year spectrograms for some stations that revealed an increase of ASN in the 2-5 Hz frequency range during the warmer seasons, contrary to the colder months. On the other hand, at lower frequencies (0,5-1 Hz), the power of seismic noise increases during the colder months of the year.


Acknowledgement:
This work has been accomplished within the NUCLEU Program supported by the Ministry of Research, Innovation and Digitization, MULTIRISC project, project PN1908020.