Characterizing Broadband Seismic Noise in Central London

Abstract

Recordings made at five broadband seismometers, deployed in central London during the summer of 2015, reveal the wideband nature (periods, T , of between 0.01 and 100 s) of anthropogenic noise in a busy urban environment. Temporal variations of power spectral density measurements suggest transportation sources generate the majority of the noise wavefield across the entire wideband, except at the secondary microseismic peak (2< T <6 s). The effect of road traffic is greatest at short periods (T <0.4 s) where acceleration noise powers are ∼20 dB larger than the New High Noise Model; at T =0.1 s daytime root-mean-square acceleration amplitudes are 1000 times higher in central London than at an observatory station in Eskdalemuir, Scotland. Overground railways generate observable signals both at short periods (T <0.3 s), which are recorded in close proximity to the tracks, and at very long periods (T >20 s) which are recorded across the city. We record a unique set of signals 30 m above a subway (London Underground) tunnel interpreted as a short-period dynamic component, a quasi-static response to the train moving underneath the instrument, and a very long period (T>30 s) response to air movement around the tunnel network. A low-velocity clay and sand overburden tens of metres thick is shown to amplify the horizontal component wavefield at T ∼1 s, consistent with properties of the London subsurface derived from engineering investigations. We provide tabulated median power spectral density values for all stations, to facilitate comparison with any future urban seismic deployments.

Urban Seismology: on the origin of earth vibrations within a city

“…4a ). At high frequencies, individual passages of subway trains are recognized in the 20–40 Hz band, coherently to observations described in different cities worldwide, as Cologne 22 , Long Beach 7 , Beijing 24 , London 11 or Auckland 10 . Figure 4a shows a clear relationship between the observed peaks and train passages, with in the passage interval increasing progressively after 22:00 local time and during Saturdays and Sundays.…”

“…Recently, Green et al . 11 have analyzed a network of 5 broad-band seismometers operated in central London during about one month. Again, human generated signals dominate most of the seismic spectra, except for the microseismic secondary peak (0.16–0.5 Hz) and vibrations related to subway circulation are observed both at high and low frequencies.…”

Ambient Vibrations of Age-old Masonry Towers: Results of Long-term Dynamic Monitoring in the Historic Centre of Lucca

“…Long-term monitoring plays an important role when a structure is subjected to high vibration levels, such as those induced by traffic or construction sites (Wyjadlowski, 2017), or when the structure is located in high-seismicity areas (Celebi, 2017, Todorovska, 2009, Trifunac, 1970. More recently, the study of the dynamic effects on buildings of the surrounding environment has became a challenging research topic, involving disparate expertise from the fields of physics, geology and engineering, and sometimes referred to as "urban seismology" (Diaz et al, 2017), (Green et al, 2016), (Ritter et al 2005). Moreover, the recent availability of low-cost measurement devices has encouraged the testing of large accelerometer networks for monitoring purposes (Barsocchi et al, 2018), (D'Alessandro et al, 2018), (Clementi et al, 2018), including through participative approaches as in (Matarazzo et al, 2018), where citizens were directly involved in monitoring the vibrations of bridges with their own smartphones (which are normally equipped with MEMS devices to measure accelerations).…”

Temporal changes in anthropogenic seismic noise levels associated with economic and leisure activities during the COVID-19 pandemic

“…Based on these characteristics we de ned ve frequency classes, and classi ed the average noise level at each station in these. Even with anthropogenic seismic noise, the averaged noise level strongly re ected the ease of shaking or the ampli cation due to the soft sediments [21][22][23] . McNamara and Buland 3 observed the strongest noise levels in the frequency range >1 Hz due to the large human population in the United States, however, at the scale of our study, the geological effect (i.e., soft sediments) was larger.…”

“…These correspond to the youngest sediments 21 . The noise level strength likely re ected the ease of shaking or ampli cation due to soft sediments 22,23 . The energy in the frequency range >20 Hz was much smaller than that for the lower frequency range.…”