Data Services Newsletter

Volume 23 : No 2 : Summer 2021

Synthetic seismograms for Mars – IRIS DMC Synthetics Engine (Syngine)

In response to our user community requests, we have enhanced our Synthetics Engine (Syngine) service to provide synthetics for Mars quakes from two InSight Mars models and selected older Mars models. This extended Syngine service complements the other IRIS DMC Mars-related services (Mars InSight mission data access and mars-event Service).

What’s new

InSight mission Mars models from ETH Zurich database

The InSight mission presents two Syngine databases for Mars based on the crust (Knapmeyer-Endrun et al., 2021), mantle (Khan et al. 2021), and core (Stähler et al., 2021a). The models are based on two different inversion methods taking into account constraints from mineralogy and thermodynamics. The inversion data are:

  1. body wave picks (P, S, PP, SS, PPP, SSS, ScS)
  2. Mean density of the planet and moment of inertia
  3. 2nd order tidal Love number k2
  4. Receiver function-derived crustal layering

The first model, InSight_KKS21GP, is based on a “geophysical” inversion allowing for 6 different bulk compositions, using an adiabatic temperature profile below the lithosphere (Khan et al. 2021). The second model, InSight_KKS21GD, is based on a “geodynamic” inversion that simulates 4 billion years of thermal convection, but is restricted to a single compositional model (described in SM8 in Stähler et al., 2021a). Both models show the same misfit against data, but are just two models out of 200 results of a MCMC (Mars Climate Modeling Center) run (for full dataset information see Stähler et al., 2021b). Since these inversions did not use receiver functions to constrain the crustal profile, a crust similar to that of Knapmeyer-Endrun et al., 2021) was added manually.

The attenuation structure has been fixed to:

  • Qmu=100 in the upper crustal layer 0-10 km (to suppress reverberations above the strong inner crustal boundary)
  • Qmu=300 between 10 km and 180 km
  • Qmu=600 in the mantle below 180 km
  • Qkappa=1e5 at reference period of 1 second

Note that the synthetic data shows a relatively clear surface wave train up to the highest frequencies, which in reality would be suppressed by scattering.

The papers describing the dataset can be openly accessed at:
https://mars.nasa.gov/insight/mission/science/research-papers/

Example

Similar to usage for the Earth models, a single Syngine request for a single-source and single-model returns all synthetics in a ZIP archive containing SAC or miniSEED files. The following figure is produced by plotting the SAC output (saczip) of the following request that uses the InSight_KKS21GD model:

http://service.iris.edu/irisws/syngine/1/query?model=mars_insightkks21gd_2s&label=mars_demo_gd&format=saczip&components=ZNE&units=displacement&origintime=2021-01-01T00:00:00&receiverlatitude=10.0&receiverlongitude=20&sourcelatitude=0&sourcelongitude=0&sourcedepthinmeters=50000 &sourcedoublecouple=310,15,90,1E19 &networkcode=SY&stationcode=IGD&locationcode=00&nodata=404

Mars Synthetic
Sample plot of a three component SAC output of the above Syngine request.

Syngine overview

http://ds.iris.edu/ds/products/syngine/

Web Service documentation & examples

https://service.iris.edu/irisws/syngine/1

Web service URL builder

https://service.iris.edu/irisws/syngine/docs/1/builder/

Acknowledgements

IRIS Data Products would like to thank the following for their support in making this new Syngine capability possible:

  • ETH Zurich, particularly Martin van Drie and the Marsquake Service (MQS) team, for allowing IRIS to access their model database and Instaseis server (Ceylan et al, 2017) as the Syngine backend.
  • Instaseis authors and Lion Krischer for help to incorporate necessary changes in the Instaseis package to support geocentric SAC header.
  • The InSight models were created with the help of Amir Khan, Mélanie Drilleau, and Cecilia Duran.

References

InSight models:

  • Khan et al. 2021. Upper mantle structure of Mars from InSight seismic data. Science 373 (6553): 434-438; doi:10.1126/science.abf2966
  • Knapmeyer-Endrun et al., 2021. Thickness and structure of the martian crust from InSight seismic data. Science 373 (6553): 438-443; doi:10.1126/science.abf8966
  • Stähler et al., 2021a. Seismic detection of the martian core. Science 373 (6553): 443-448; doi:10.1126/science.abi7730
  • Stähler et al., 2021b. Interior Models of Mars from inversion of seismic body waves (Version 1.0). IPGP Data Center; doi:10.18715/IPGP.2021.kpmqrnz8

ETH web services:

  • Ceylan, S., M. van Driel, F. Euchner, A. Khan, J. F. Clinton, L. Krischer, M. Boese, S. Staehler, and D. Giardini (2017). From initial models of seismicity, structure and noise to synthetic seismograms for Mars, Space Science Reviews, InSight Special Issue, doi:10.1007/s11214-017-0380-6.

Information on Mars models available from Syngine:

  • Clinton, J. F., D. Giardini, P. Lognonné, B. Banerdt, M. van Driel, M. Drilleau, N. Murdoch, M. Panning, R. Garcia, D. Mimoun, M. Golombek, J. Tromp, R. Weber, M. Böse, S. Ceylan, I. Daubar, B. Kenda, A. Khan, L. Perrin, A. Spiga; Preparing for InSight: An Invitation to Participate in a Blind Test for Martian Seismicity. Seismological Research Letters 2017; 88 (5): 1290–1302. doi:10.1785/0220170094

IRIS DMC Syngine data product:

by Data Products (IRIS DMC) , Simon Stähler (ETH Zurich) and Marsquake Service (MQS) team (ETH Zurich)

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