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Start Over Descriptor "mikroseizmički nemir" Topic microtremor
2 results on '"mikroseizmički nemir"'

1. The assessment of local site effects and dynamic behaviour in Nicosia, Cyprus.

Author

Dindar, Hilmi, Akgün, Mustafa, Atalar, Cavit, and Özdağ, Özkan Cevdet

Subjects
*SEISMIC waves, *EARTHQUAKE zones, *SHEAR waves, *PLATE tectonics, *SOIL mechanics
Abstract

Single-station microtremor measurements were conducted to investigate earthquake and soil behaviour for the first time in Nicosia, Cyprus. Cyprus is located in a tectonically complex area in the Eastern Mediterranean where three plates meet. The study area was chosen to cover the areas to be opened for new development. Nicosia, the capital of Cyprus, is also the island's most important cultural, industrial, commercial, and transportation centre. The study creates base maps for the soil to assess earthquake resistance crucial for construction. Microtremor Method was applied at 100 stations and the Multi-Channel Analysis of Surface Waves (MASW) method was used at 52 stations. Also, Refraction-Microtremor (Re-Mi) and L-Shaped Spatial Autocorrelation (L-SPAC) methods were carried out at 17 stations to substantiate the research. The results of the microtremor method indicate that the predominant soil period values have an average of 1 second and pre-dominant peak period values are generally found between 0.1 to 5 s at the study area. Peak amplitude values are observed between 1 and 2.4. The Vulnerability Index Parameter (Kg) exceeded 20 at the central and the southern stations, and Kg values change between 7 and 54 units. The Kg values were found to be higher than 20 in soils where shear wave velocity is lower than 760 m/s. At the same time, the values of the predominant peak period were greater than 1 second. Cyprus is located in the Alpine Himalayan earthquake zone. The Cyprus Arc is known as the main seismic source of the island, It constitutes the tectonic border among African and Eurasian lithospheric plates in the region. During an earthquake in Nicosia, seismic waves will be amplified by an average of 1.5 times and soil deformation will occur due to the exceeding elastic limits. The results provided important insight into soil behaviour and indicated its reactions in a potential earthquake. [ABSTRACT FROM AUTHOR]

Published
2021
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2. PROCJENA ODZIVA TLA MJERENJEM MIKROSEIZMIČKOG NEMIRA U GRADU VARAŽDINU

Author

Davor Stanko, Stjepan Strelec, Mario Gazdek, Alen Filipović, and Nikola Kaniški

Subjects
mikroseizmički nemir, odziv tla, rezonantna frekvencija tla, faktor amplifikacije, urbano planiranje, microtremor, site effects, resonant frequency of soil, amplification factor, urban planning
Abstract

Na jačinu podrhtavanja tla na nekoj lokaciji za vrijeme potresa osim njegove magnitude i udaljenosti spomenute lokacije od epicentra potresa, utječu i efekti lokalnog tla. Prilikom širenja seizmičkih valova kroz tlo dolazi do amplifikacije (engl. amplification) seizmičke pobude od osnovne stijene (engl. bedrock) do površine tla (engl. surface ground). Metoda mjerenja mikroseizmičkog nemira, tzv. HVSR metoda (engl. Horizontal-to-Vertical Spectral Ratio), u posljednja dva desetljeća pokazala se kao brza i jednostavna metoda za istraživanje odziva tla, tj. za određivanje rezonantne frekvencije tla i faktora amplifikacije. Mikroseizmički nemir može se definirati kao stalno podrhtavanje tla Zemlje uzrokovano prirodnim (vjetar, oceanski valovi, daleki potresi, ciklone i anticiklone) i umjetnim (promet, industrijski strojevi) izvorima. U ovom radu prikazan je princip metode mjerenja mikroseizmičkog nemira u procjeni odziva tla na području grada Varaždina. Rezultati mjerenja su uspoređeni s postojećim bušotinama u u gradu i izvan grada. Uočena je veoma jaka povezanost između geološke strukture i izmjerenih frekvencija i amplifikacija lokalnog aluvijalnog tla. HVSR metoda pogodna je za brzu i efikasnu procjenu rezonantne ili osnovne frekvencije tla f0 te procjenu amplifikacije HVSR(f) = A(f) u području niske seizmičnosti poput grada Varaždina. Procjena odziva lokalnog tla veoma je važno kod urbanog planiranja, procjene seizmički opasnih zona u gradskim područjima, za aseizmičko projektiranje, kao i za potencijalnu seizmičku procjenu obnove povijesnih građevina., A local site effect also affects intensity of soil vibration during an earthquake except of magnitude and epicenter distance from earthquake. When seismic wave propagates through soil, it comes to the amplification of seismic ground motion from bedrock to ground surface soil. In the last two decades, microtremor measurements method, e.g. HVSR (Horizontal-to-Vertical Spectral Ratio) has been showed as fast and simple method for assessment of local site effects, i.e. determination of resonant soil frequencies and soil amplification factors. Microseismic noise can be defined as a continuously Earth tremor caused by natural (wind, ocean waves, long earthquakes, cyclones and anticyclones) and artificial (traffic, industrial machines) sources. In this paper we demonstrate use of microtremor measurement method for assessment of local site effect in Varaždin city. Given results are compared to the existed boreholes inside and outside the city and a strong correlation have found between geological structure and measured frequencies and amplifications of local alluvial soil. HVSR method proved to be useful for fast and efficient assessment of resonant soil frequency f0 and soil amplification HVSR(f) = A(f) in an area of low seismicty like Varaždin city. Assessment of local site effects is very important for urban planning, assessment of seismic danger zones in city area, for aseismic building construction, and also for potential sesimic evaluation of historical building retrofiting.

Published
2015

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