Ambient noise cross-correlation functions and three-dimensional S-wave velocity structure in the Noto Peninsula, Japan
Abstract
The three-year-lasting earthquake swarm in the Noto Peninsula, Japan, led to the 2024 Noto earthquake (moment magnitude 7.5). To reveal structural controls on the swarm evolution and the large earthquake generation, we imaged the three-dimensional S-wave velocity structure beneath the Noto Peninsula using ambient noise surface wave tomography with dense seismic observations. This dataset provides the cross-correlation functions of the densely observed ambient seismic noise and the estimated three-dimensional S-wave velocity structure model. We computed the multicomponent cross-correlation functions for the pairs of 22 seismic stations (composed of 12 seismic nodes and 10 short-period permanent stations). The observation data spanned 32 days, from October to November 2023. The cross-correlation functions in the vertical-vertical, vertical-radial, radial-radial, and transverse-transverse components yielded the estimates of dispersion curves of Rayleigh and Love waves. The dispersion curves of the fundamental-mode Rayleigh and Love waves in the frequency range of 0.10–0.45 Hz were used to estimate isotropic S-wave velocity structure via two-dimensional phase velocity tomography and a series of local 1D inversions. Our results show a high-velocity body collocated with the major slip zone of the 2024 Noto earthquake, a region the preceding swarm avoided. This observation strongly suggests that the structural heterogeneity beneath the Noto Peninsula controlled the swarm evolution and the generation of the 2024 Noto earthquake.
https://doi.org/10.5061/dryad.zcrjdfnm3
Description of the data and file structure
ccf.h5: The cross-correlation function (CCF) data are stored in the self-describing HDF5 format. The attributes of the HDF5 file describe the following parameters:
- b: Starting lag time of CCFs in seconds (-204.7).
- nc: Number of components of original seismograms (3). The number of CCF components is nc x nc (9).
- ns: Number of stations (22).
- npts: Number of CCF data samples (4096).
- sr: Sampling rate in samples per second (10).
- stnm1 & stnm2: Names of stations 1 & 2.
- stla1 & stla2: Latitudes of stations 1 & 2.
- stlo1 & stlo2: Longitudes of stations 1 & 2.
- stel1 & stel2: Elevations of stations 1 & 2.
- cmpnm: Name of CCF component.
- nstack: Number of CCF stacks.
vs3d.nc: The 3D S-wave velocity model is stored in the NetCDF format. This file contains three variables as follows:
- Vs: Estimated S-wave velocity in km/s.
- Ndata: Number of dispersion data used to estimate S-wave velocity. At grid points with zero Ndata, the S-wave velocity structures are the same as the initial model (Nishida et al. 2008; doi:10.1029/2007JB005395).
- SD: Standard deviation of the estimated S-wave velocity in km/s.
