Olszewska, Dorota and Mutke, Grzegorz (2018) A STUDY OF SITE EFFECT USING SURFACE-DOWNHOLE SEISMIC DATA IN A MINING AREA. In: 16th European Conference on Earthquake Engineering, 18-21 June 2018, Thessaloniki, Greece.
|
Text
Olszewska_Mutke_1ECEE_fin2_20180305.pdf - Submitted Version Download (2MB) | Preview |
Abstract
The aim of this study is to examine the phenomenon of site effect using surface-downhole seismic data caused by mining tremors in the Upper Silesia Coal Basin (USCB). The USCB is located in southern Poland and as a consequence of underground mining operations about 1000 mining tremors occur annually with a local magnitude of ML≥1.5. The strongest event which occurred on 09.02.2010 reached ML=4.2 and the peak ground acceleration (PGA) observed was approximately – 2 m/s2. Induced events which can be treated as minor shallow earthquakes also have an impact on the surface. Thus, monitoring of ground motion is carried out and provided by the Central Mining Institute in this area – the Upper Silesian Seismological Network USSN (data are available as “episode USCB” on the IS-EPOS platform at https://tcs.ah-epos.eu/). Analysis of the site effect was done using data from two stations each containing 2 sensors, one on the surface and one 30 m downhole. The station includes one accelerometer on the surface and one in the 30 m downhole. This study was done using ground motion recordings of underground mining events with ML≥2.3 from January 2014 to June 2017. In the first step, the amplification factors were calculated as a ratio between the surface and downhole PGA. Next, transfer functions of both components were calculated using surface and downhole data and HVSR (Horizontal to Vertical Spectral Ratio) curves were obtained. All those results were compared with each other, particularly in terms of the impact of the vertical component. Profiles of sheer waves up to 30 m were also used in this study. The result shows that the vertical component is amplified in a different manner to that of the horizontal. Moreover, the results of these analyses allow for a better understanding of the amplification phenomena caused by the surface layer in this area.
| Item Type: | Conference or Workshop Item (Paper) |
|---|---|
| Uncontrolled Keywords: | amplification, downhole measurement, HVSR, transfer function |
| Subjects: | Methodology > Method and procesing > Probabilistic seismic hazard analysis - stationary > Path and site effects Region > Poland > Legnica-Glogow Copper District Inducing technology > Underground mining |
| Project: | IS-EPOS project > USCB: Regional seismicity and ground motion associating underground coal mining EPOS-IP > USCB: Regional seismicity and ground motion associating underground coal mining |