Effects of shallow-layer reverberation on measurement of teleseismic P-wave travel times for ocean bottom seismograph data

Abstract

We conducted synthetic experiments to evaluate the effects of shallow-layer reverberation in oceanic regions on P-wave travel times measured by waveform cross-correlation. Time shift due to waveform distortion by the reverberation was estimated as a function of period. Reverberations in the crystalline crust advance the P-waves by a frequency-independent time shift of about 0.3 s in oceans. Sediment does not affect the time shifts in the mid-ocean regions, but effects as large as −0.8 s or more occur where sediment thickness is greater than 600 m for periods longer than 15 s. The water layer causes time delays (+0.3 s) in the relatively shallow (<3500 m) water region for periods longer than 20 s. The time shift may influence mantle images obtained if the reverberation effects are not accounted for in seismic tomography. We propose a simple method to correct relative P-wave travel times at two sites for shallow-layer reverberation by the cross-convolution of the crustal responses at the two sites.

Characterizing the Seafloor Sediment Layer Using Teleseismic Body Waves Recorded by Ocean Bottom Seismometers

“…Our method for constraining P‐wave reverberations can better predict the effect of P‐wave reverberations in the vertical‐component waveforms. This improved predictability is important because reverberations cause frequency‐dependent travel‐time shifts, which are critical in finite frequency travel‐time analyses (e.g., Obayashi et al., 2017).…”

“…In receiver function analysis, the phases from the sediment layer not only interfere with the deeper structural signals (e.g., Audet, 2016; Kawakatsu & Abe, 2016) but also increase the instability in the deconvolution process (Akuhara et al., 2021). Reverberations from the sediment layer also influence the frequency‐dependent arrival‐time measurements, which must be appropriately corrected to conduct deeper mantle studies (Obayashi et al., 2017). Furthermore, thick seafloor sediment cover inhibits the use of seafloor compliance and surface‐wave measurements to investigate the oceanic crust and mantle structures (e.g., Ball et al., 2014).…”

Global finite-frequency S-wave delay-times: how much crust matters

“…Finally, we show that the finite-frequency part of the correction cannot be neglected compared to the ray-theory part. Except for Obayashi et al (2004Obayashi et al ( , 2017, previous studies, aiming at correcting those crustal finite-frequency effects, have used a synthetic pre-computed correction and applied it after the measurement process (e.g., Hosseini & Sigloch 2015). We quantitatively show that a better way to deal with crustal FF effects is to include crustal multiples directly in synthetics before the measurement process.…”

“…These interferences between crustal phases and the target seismic phase depend on the crustal structure and the dominant period used to filter seismograms (e.g., Ritsema et al 2009). To our knowledge, a few email: fredericdubois@unistra.fr previous studies have investigated these crustal effects on "broad-band" filtered seismic waveforms (usually the 2-50 s period range for S-waves) (e.g., Fukao et al 2003;Obayashi et al 2004;Ritsema et al 2009;Kolstrup & Maupin 2015;Obayashi et al 2017). Moreover, some of them investigated crustal reverberations in specific geological contexts, like oceanic domain Obayashi et al 2017), or South Scandinavia (Kolstrup & Maupin 2015), what may limit the assessment of crustal reverberations, and their effect on seismic data for other geological settings.…”

Interrelation of the stagnant slab, Ontong Java Plateau, and intraplate volcanism as inferred from seismic tomography

“…We measured more than 170,000 differential traveltimes as a function of frequency between any two stations by multiband cross-correlation of P waveforms in pass-bands between dominant periods of 30 and 2.7 s, as well as approximately 4400 absolute traveltimes picking. We considered the effects of the reverberation through the different structures of the crusts under the two stations on multi-frequency traveltimes 43 , 44 . We also measured approximately 500 PP–P differential traveltimes whose PP rays bounced on the surface over the OJP and its vicinity using global stations 45 (red points in Fig.…”