Amplification Behaviour of Compressional Waves in Unconsolidated Sediments

Similar to horizontal earthquake motions, vertical motions are amplified depedent on the local site conditions which can be critical for safety of certain structures. Production natural gas in Groningen, Netherlands, results reservoir compaction causing low magnitude, shallow earthquakes recorded with a borehole seismic network. These recordings form an excellent data set understand how unconsolidated subsurface geology influences amplification behaviour compressional waves (P-waves). First, we present and single-station techniques (amplification factors, empirical transfer functions (ETF) V/H spectral ratio implementations) quantify amplification. We show that vertical-wave incidence is reasonable assumption. All capable emphasising sites strong ground motion during earthquake. Subsequently, compare ETF methods aim develop proxies site-response using ratios. In second step, link conditions, like P-wave velocity peat content. To better mechanisms, analytically simulate propagation. simulations, compute synthetic realistic make comparison ETF. The simulations support hypothesis thin layers gas, originating from Holocene peat, result wave observe particular eastern part industrial facilities pipeline infrastructure region. Here, if high amplifications persistent at large magnitudes, appreciable levels loading may expected. This study demonstrates should assessed separately given P-waves affected by distinctive mechanisms.