scholarly journals Oceanic high-frequency global seismic wave propagation with realistic bathymetry

2020 ◽  
Author(s):  
Benjamin Fernando ◽  
Kuangdai Leng ◽  
Tarje Nissen-Meyer
Keyword(s):  
Wave Propagation ◽  
Seismic Wave ◽  
High Frequency ◽  
Seismic Wave Propagation

scholarly journals Modelling high-frequency seismograms at ocean bottom seismometers: effects of heterogeneous structures on source parameter estimation for small offshore earthquakes and shallow low-frequency tremors

2020 ◽  
Vol 223 (3) ◽  
pp. 1708-1723
Author(s):  
Shunsuke Takemura ◽  
Suguru Yabe ◽  
Kentaro Emoto
Keyword(s):  
Wave Propagation ◽  
Parameter Estimation ◽  
Seismic Wave ◽  
High Frequency ◽  
Source Parameters ◽  
Low Frequency ◽  
Accretionary Prism ◽  
Seismic Wave Propagation ◽  
Source Parameter ◽  
Seismic Events

SUMMARY The source characteristics of offshore seismic events, especially regular (or fast) and slow earthquakes, can provide key information on their source physics and frictional conditions at the plate boundary. Due to strong 3-D heterogeneities in offshore regions, such as those relating to sea water, accretionary prism and small-scale velocity heterogeneity, conventional methods using a 1-D earth model may mis-estimate source parameters such as the duration and radiation energy. Estimations could become severe inaccuracies for small offshore seismic events because high-frequency (>1 Hz) seismograms, which are strongly affected by 3-D heterogeneities, are only available for analysis because of their signal-to-noise ratio. To investigate the effects of offshore heterogeneities on source parameter estimation for small seismic events, we analysed both observed and simulated high-frequency seismograms southeast off the Kii Peninsula, Japan, in the Nankai subduction zone. Numerical simulations of seismic wave propagation using a 3-D velocity structure model clarified the effects of each heterogeneity. Comparisons between observations and model simulations demonstrated that the thick low-velocity accretionary prism has significant effects on high-frequency seismic wave propagation. Especially for shallow low-frequency tremors occurring at depths just below the accretionary prism toe, seismogram durations are significantly broader than an assumed source duration, even for stations with epicentral distances of approximately 10 km. Spindle-shape seismogram envelopes were observed even at such close stations. Our results suggest that incorporating 3-D heterogeneities is necessary for practical estimation of source parameters for small offshore events.

scholarly journals Oceanic high-frequency global seismic wave propagation with realistic bathymetry

2020 ◽  
Vol 222 (2) ◽  
pp. 1178-1194
Author(s):  
Benjamin Fernando ◽  
Kuangdai Leng ◽  
Tarje Nissen-Meyer
Keyword(s):  
Wave Propagation ◽  
Seismic Wave ◽  
High Frequency ◽  
Seismic Wave Propagation ◽  
Global Ocean ◽  
Data Sets ◽  
Ocean Bottom ◽  
Seafloor Topography ◽  
Ocean Loading ◽  
Ocean Layer

SUMMARY We present a new approach to simulate high-frequency seismic wave propagation in and under the oceans. Based upon AxiSEM3D, this method supports a fluid ocean layer, with associated water-depth phases and seafloor topography (bathymetry). The computational efficiency and flexibility of this formulation means that high-frequency calculations may be carried out with relatively light computational loads. A validation of the fluid ocean implementation is shown, as is an evaluation of the oft-used ocean loading formulation, which we find breaks down at longer periods than was previously believed. An initial consideration of the effects of seafloor bathymetry on seismic wave propagation is also given, wherein we find that the surface waveforms are significantly modified in both amplitude and duration. When compared to observed data from isolated island stations in the Pacific, synthetics which include a global ocean and seafloor topography appear to more closely match the observed waveform features than synthetics generated from a model with topography on the solid surface alone. We envisage that such a method will be of use in understanding the new and exciting ocean-bottom and floating seismometer data sets now being regularly collected.

Lateral variations of high-frequency seismic wave propagation at regional distances across the Turkish and Iranian plateaus

1981 ◽  
Vol 86 (B10) ◽  
pp. 9377-9396 ◽  
Author(s):  
Katharine Kadinsky-Cade ◽  
Muawia Barazangi ◽  
Jack Oliver ◽  
Bryan Isacks
Keyword(s):  
Wave Propagation ◽  
Seismic Wave ◽  
High Frequency ◽  
Seismic Wave Propagation ◽  
Lateral Variations
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