Data Services Products: ondemandsynthetics On demand custom 3D AxiSEM synthetic seismograms

Summary

The Synthetics Engine (syngine) service provides access to custom tailored synthetic seismograms.

****IN DEVELOPMENT. This page is for developers. Please go HERE instead****

Description


The SYNGINE product page is now here. This page is defunct.


IN DEVELOPMENT Target release: late 2015.

The IRIS Synthetics Engine (syngine) is a webservice that quickly returns synthetic seismograms custom requested by the user. The IRIS DMC stores precalculated TB scale databases of Green’s Functions for several different 1D reference models. The Green’s Functions were generated by Tarje Nissen-Meyer & colleagues using AxiSEM (Nissen-Meyer et al., 2014), a axi-symmetric spectral element method for 3D (an-)elastic, anisotropic and acoustic wave propagation in spherical domains. It requires axisymmetric background models and runs within a 2D computational domain, thereby reaching all desired highest observable frequencies (up to 2Hz) in global seismology. The requested synthetic seismograms are calculated using instaseis (van Driel et al., 2015), a python library built for storing wavefield databases with a fast extraction algorithm. Radiation pattern, attenuation and discontinuities are all appropriately honored in the seismograms. By using instaseis and obspy, syngine provides users with fully customizable synthetic seismograms for any source-receiver combination with a variety of source options including point source or user supplied moment tensors (or GCMT), source-time functions, and finite-fault model (or from the USGS).

AxiSEM, instaseis, obspy people are welcome to modify anything here.

Models

Current models:

Model name resolution (s) dt (s) length (s) components notes database size 1D model
prem_ani 20-100 4.87 1797 vertical and horizontal 20s_PREM_ANI_FORCES for testing only 0.6 GB (link)
ak135f 2-100 0.487 3700 vertical and horizontal 1.0 TB (link)
iasp91 2-100 0.483 3700 vertical and horizontal 1.3 TB (link)
prem_iso 2-100 0.488 3700 vertical and horizontal isotropic 1.1 TB (link)

Possible future models:

  • Feedback welcome!
  • From what I understand, water layer models would put receivers on ocean floor. Can this be made to capture water reverberations generated on the source side (desirable), but not on the receiver side (not desirable)? Martin mentioned a different (i.e. continental) crust for receivers would be difficult but may be possible, any progress/thoughts on this?
  • We’ll use either prem_5s or prem_10s for the FFM service, TBD.
  • names limited to 8 characters, due to SAC header limit.

Model name resolution (s) dt (s) length (s) components notes database size 1D model
ak135f_p 1-100 1.0 1900 vertical high res for P-waves ~1 TB (link)
prem_cnt 2-100 0.5 3700 vertical and horizontal PREM w continental crust ~1 TB (link)
prem_ocn 2-100 0.5 3700 vertical and horizontal PREM w oceanic crust ~1 TB (link)
prem_ow1 5-100 0.5 3700 vertical and horizontal PREM w oceanic crust and 1 km water layer ~25 GB (link)
prem_ow3 5-100 0.5 3700 vertical and horizontal PREM w oceanic crust and 3 km water layer ~25 GB (link)
prem_ow5 5-100 0.5 3700 vertical and horizontal PREM w oceanic crust and 5 km water layer ~25 GB (link)
prem_ani 5-100 0.2 3700 vertical and horizontal anisotropic PREM ~25 GB (link)
prem_5s 5-100 0.2 3700 vertical and horizontal for separate FFM service ~25 GB (link)
prem_10s 10-100 0.1 3700 vertical and horizontal for separate FFM service ~5 GB (link)
prem_3hr 5-100 0.5 10900 vertical and horizontal extends out to 3 hours ~75 GB (link)

Building a request

Details and a URL builder are available here.

Raw Green’s functions:

AxiSEM requires a finite source; to achieve an approximation of the raw Green’s functions, the input source is deconvolved from the synthetic seismogram.

Sourcewidth:

Scaled by moment if the scalar moment exceeds a model-resolution dependent threshold???

Geographic/Geocentric Latitudes:

AxiSEM and instaseis, which drive syngine, use geocentric latitudes. Station and earthquake coordinates use geographic latitudes. It is common practice in seismology to convert from geographic to geocentric latitudes in order to calculate distance using spherical geometry. Syngine also does this. The discrepancy between the two latitude types is at most only a fifth of a degree (~22 km) and not significant for most users given the resolution of the available models. More on latitude

Choosing a new sampling rate:

In order to avoid aliasing, downsampling is not allowed by instaseis, only upsampling. If a model has a default dt=0.5, dt=0.1 is allowed, dt=1.0 is not allowed.

Finite-fault model sources and custom source-time functions:

Syngine can also calculate synthetic seismograms for finite-fault model (FFM). The FFM must be in .param format (http://example) and available from a URL. Custom source-time functions for the source are also supported with a URL to a two-column file with time and amplitude. Any input FFM or STF will automatically be low-pass filtered to an appropriate model resolution limited bandwidth in order to avoid aliasing. This service is on a separate endpoint.

examples:

http://service.iris.edu/irisws/synginestf/1/query?network=IU&station=ANMO&components=Z&starttime=2010-02-27T06:30:00.000&endtime=2010-02-27T10:30:00.000&stffile=chile.stf.txt (((( NOT YET SUPPORTED )))

http://service.iris.edu/irisws/syngineffm/1/query?network=IU&station=ANMO&components=Z&starttime=2010-02-27T06:30:00.000&endtime=2010-02-27T10:30:00.000&ffmfile=chile.param.txt (((( NOT YET SUPPORTED )))

Citations and DOIs

Nissen-Meyer, T., van Driel, M., Stähler, S. C., Hosseini, K., Hempel, S., Auer, L., Colombi, A., and Fournier, A.: AxiSEM: broadband 3-D seismic wavefields in axisymmetric media, Solid Earth, 5, 425-445, http://doi:10.5194/se-5-425-2014, 2014.

van Driel, M., Krischer, L., Stähler, S. C., Hosseini, K., and Nissen-Meyer, T.: Instaseis: instant global seismograms based on a broadband waveform database, Solid Earth, 6, 701-717, http://doi:10.5194/se-6-701-2015, 2015.

Credits

Tarje Nissen-Meyer (University of Oxford)
Martin van Driel (ETH Zürich)
Lion Krischer (Munich University)
Simon Stähler (Munich University)
Kasra Hosseini (Munich University)

Contributors

Tarje Nissen-Meyer
ETH Zurich

Contact

Categories

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Syngine