Models
Our research involves the development of models in a broad sense, including models of the Earth's interior, ice sheets, and seismic sources. Below you can find a collection of such models with download links.
Hot models (> 0 °C)
- FWI of the African Plate
- Long-wavelength Earth model (LOWE)
- Collaborative Seismic Earth Model (CSEM) generation 1
Cool models (< 0 °C)
Stormy models
FWI of the African Plate
This full seismic waveform inversion of the African Plate was constructed using the combination of spectral-element wavefield simulations, adjoint techniques and stochastic mini-batch optimisation. We performed 130 iterations and invert data from 397 unique earthquakes and 184,356 unique source-receiver pairs. The minimum period is 35 s. We clearly image tectonic features such as the Afar triple junction. Particularly interesting are the low-velocity zones below the Hoggar, Aïr, and Tibesti Mountains, pronounced more than in earlier works. Finally, we introduce a new strategy to assess model uncertainty. We deliberately perturb the final model, perform additional mini-batch iterations, and compare the result with the original final model. This test uses actual seismic data instead of artificially generated synthetic data and requires no assumptions about the linearity of the inverse problem.
Resources:
- Model in hdf5 format
- Model in NetCDF format (compatible with IRIS EMC)
Publications:
- external pageFull-waveform tomography of the African Plate (van Herwaarden et al., JGR 2023)
Long-wavelength Earth Model (LOWE)
The LOng-Wavelength Earth model (LOWE) is a whole-Earth model of radially anisotropic seismic structure. It has been constructed using full-waveform inversion with wavefield-adapted meshes. Working at periods between 100 - 200 s, it assimilates complete three-component seismic waveforms from 1179 earthquakes.
Resources:
The model can be downloaded in two different formats:
- NetCDF for use in the external pageIRIS EMC (here)
- HDF5 for use in external pageSalvus simulations (here)
Publications:
- external pageData-adaptive global full-waveform inversion (Thrastarson et al., GJI 2022)
- external pageAccelerating numerical wave propagation by wavefield adapted meshes. Part II: full-waveform inversion (Thrastarson et al., 2020)
Collaborative Seismic Earth Model
The first-generation Collaborative Seismic Earth Model (CSEM) can be downloaded most easily from the website of the external pageIRIS EMC. The second generation CSEM will become available soon.
Publications:
EastGRIP Firn Model
The external pageEastGRIP firn model has been derived using Backus-Gilbert inversion of multi-mode dispersion data. These data have been recorded with a 3 km long DAS cable during the landing of a C-130 Hercules near the EastGRIP camp. Field work impressions including the airplane landing can be found on our external pageYouTube Channel.
Resources:
- DownloadRaw DAS data and code for data analysis (visualisation, f-k analysis and dispersion curves) (ZIP, 65.7 MB)
- DownloadCode for Backus-Gilbert inversion, including a suite of possible models (ZIP, 4 MB)
Publications:
- external pageFiber-optic airplane seismology on the Northeast Greenland Ice Stream (Fichtner et al., TSR 2023)
EastGRIP Ice Sheet Seismic Model
The P and S wave speed model of the Northeast Greenland Ice Sheet near the external pageEastGRIP drill site has been computed by nonlinear traveltime inversion of active-shot seismic data recorded within the EastGRIP borehole. For the recordings, we lowered a fibre-optic cable 1'500 m into the borehole and recorded strain rate using Distributed Acoustic Sensing (DAS). Field work impressions can be found on the Yexternal pageouTube channel of our group.
Resources:
The active-shot seismic DAS data are freely available here.
The ensmble of acceptable P and S wave speed models can be found here.
Seismic ambient noise source maps
The Seismic Ambient Noise Source maps (SANS) are daily global models of the power-spectral density distribution of microseismic noise sources in the oceans. Using spectral-element wavefield simulations and asymmetry measurements on noise correlations, these maps are computed every day, thereby providing a snapshot of interactions between atmosphere, oceans and the solid Earth with high temporal and spatial resolution.
Resources:
The noise source models can be downloaded from the SANS website.
Publications:
- external pageRapid finite-frequency microseismic noise source inversion at regional to global scales (Igel et al., 2021)
- external pagePublicly available daily multi-scale seismic ambient noise source maps (Igel et al., 2023)
Frequency-dependent hum sources
The frequency-dependent hum source model provides the distribution of the power-spectral density distribution of forces at the Earth's surface that excite low-frequency ambient seismic noise.
Resources:
The complete model in vtk format can be downloaded Downloadhere.
Publications: