Figure - uploaded by Carl Tape
Content may be subject to copyright.
Source publication
Nenana basin in central Alaska is a long (90 km), narrow (12 km), and deep (7 km) sedimentary basin aligned with an active fault zone producing Mw≥6 earthquakes. From 2015 to 2019, 13 broadband seismic stations were deployed in the region as part of the Fault Locations and Alaska Tectonics from Seismicity project. These stations recorded a wide ran...
Contexts in source publication
Context 1
... analysis of Nenana basin focuses on the same 16 stations in Smith and Tape (2019a), including 13 stations from the FLATS deployment and three additional bedrock stations (AK.NEA2, TA.I23K, and AK.MLY; Fig. 1 and Table 1). Two FLATS stations (F3TN and FPAP) were installed in September 2014, whereas the remaining FLATS stations were installed in September 2015. ...Context 2
... some analyses, we use the sedimentary thickness or basin depth beneath each station. We use these depths to categorize the 13 stations into two bedrock stations (FTGH, F8KN), four marginal basin stations (FPAP, FAPT, F6TP, and F7TV), and seven basin stations (F1TN, F2TN, F3TN, F4TN, F5MN, FNN1, and FNN2; Table 1). We assign basin depths of 1 km to the four marginal basin stations that are outside the coverage of PRA (2017) but within the region of sedimentary cover and gravity low (Ehm, 1983;Kirschner, 1988). ...Context 3
... assign basin depths of 1 km to the four marginal basin stations that are outside the coverage of PRA (2017) but within the region of sedimentary cover and gravity low (Ehm, 1983;Kirschner, 1988). FTGH is categorized as "near bedrock" in Table 1 because it is near the top of a ridge, although bedrock is at an unknown depth below the sensor. ...Context 4
... each earthquake we use colored "matrix plots" to display the correlation coefficients for a large number of different bandpasses used to filter the seismograms. A set of matrix plots for all 43 local and regional earthquakes (Fig. S17) shows that 0.1-0.5 Hz Target stations F8KN NEA2 FTGH I23K MLY F3TN F4TN FNN2 F2TN F5MN F1TN FNN1 F6TP FAPT FPAP F7TV I23K NEA2 FTGH MLY Table 4. hf, high frequency; and lf, low frequency. ...Similar publications
Previous studies mainly attribute injection‐induced earthquakes (IIE) to hydraulic fracturing (HF) operations in the Western Canada Sedimentary Basin (WCSB), whereas the role of wastewater disposal (WD) has been largely overlooked. One particular reason is that HF operations usually exhibit a clearer spatiotemporal relationship to IIE than WD. Howe...
Central Java is a part of the Sunda Arc and has relatively high seismicity due to the subduction zone between the Indo-Australian Plate and the Eurasian Plate. This study uses double-difference tomography to image the P and S wave 3D seismic velocity structures associated with tectonic patterns due to subduction zones. The data used comes from the...
Citations
The amplitude and frequency content of background seismic noise is highly variable with geographic location. Understanding the characteristics and behavior of background seismic noise as a function of location can inform approaches to improve network performance and in turn increase earthquake detection capabilities. Here, we calculate power spectral density estimates in one-hour windows for over 15 yr of vertical-component data from the nine-station Caribbean network (CU) and look at background noise within the 0.05–300 s period range. We describe the most visually apparent features observed at the CU stations. One of the most prominent features occurs in the 0.75–3 s band for which power levels are systematically elevated and decay as a function of proximity to the coastline. Further examination of this band on 1679 contiguous USArray Transportable Array stations reveals the same relationship. Such a relationship with coastal distance is not observed in the 4–8 s range more typical of globally observed secondary microseisms. A simple surface-wave amplitude decay model fits the observed decay well with geometric spreading as the most important factor for stations near the coast (<∼50 km). The model indicates that power levels are strongly influenced by proximity to coastline at 0.75–3 s. This may be because power from nearshore wave action at 0.75–3 s overwhelms more distant and spatially distributed secondary microseism generation. Application of this basic model indicates that a power reduction of ∼25 dB can be achieved by simply installing the seismometer 25 km away from the coastline. This finding may help to inform future site locations and array design thereby improving network performance and data quality, and subsequently earthquake detection capabilities.
Abundant seismic waveforms have been collected in Xinjiang since 2007, following the deployment of permanent stations by the China National Seismic Network and the Xinjiang Seismic Network. We investigated regional attenuation of the S–Lg phase in the crustal waveguide and site response in Xinjiang using broadband recordings at 44 stations from 118 earthquakes with magnitudes of 4.4–7.0 occurring in Xinjiang and adjacent areas between January 2009 and February 2022. We used linear regression analysis of the Fourier acceleration amplitude spectra in 18 frequency bands from 0.1 to 24.86 Hz to estimate site response terms and distance-dependent anelastic attenuation quality factor Q in the crustal waveguide at regional distances. The regression site terms of stations located in the Tarim and Junggar Basins show significant amplification at low frequencies and strong attenuation at higher frequencies due to the presence of thick sedimentary deposits. We quantified the linear behavior of the logarithms of the high-frequency site terms versus frequency using the zero distance attenuation parameter κ0 (Anderson and Hough, 1984). A positive correlation was observed between κ0 and the thickness of the sedimentary layers in Xinjiang. We observed some consistent patterns in the behavior of the site response terms as a function of sediment thickness over the frequency range of 0.1–24.86 Hz. Linear functions of sediment thickness were used to model the site response in Xinjiang at each of the 18 frequencies. An alternative approach that adopted the κ0 model as a function of sediment thickness can be used to estimate site responses at high frequencies (≥5.66 Hz). The results of this study demonstrate the nature of site effects on earthquake ground motions caused by the thick sedimentary deposits in Xinjiang and provide a preliminary site response model as a function of sediment thickness for this region.
