Simon C. Stähler

Seismology everywhere

I'm a postdoctoral seismologist mainly interested in all the inverse problems our discipline poses: Finding out about Earth's history contained in the mantle, about the sources of earthquakes and what that tells us about the tectonic situation of places.

Part of my interest is the epistemological question to find out how much we actually can find out given the observations we have. Since Earth science tries to infer the billion year history of the whole earth just from some scrambled observations at the very surface of the planet, which all happen to happen now, that's a rather curious task.

Recent publications

and why you should be interested

Fully probabilistic seismic source inversion – Part 2: Modelling errors and station covariances

The long-awaited sequel

How can we construct a Likelihood function for non-Gaussian noise on seismic waveforms? Turns out that the dependable Correlation Coefficient follows a log-normal distribution, so we can use that.

**Stähler, S. C.**, K. Sigloch,**Fully probabilistic seismic source inversion – Part 2: Modelling errors and station covariances**, in public review for*Solid Earth*Performance report of the RHUM-RUM ocean bottom seismometer network around La Réunion, western Indian Ocean

Overview of OBS performance in the RHUM-RUM project, especially in comparison between the German (DEPAS) and the French (INSU) seismometers.

**Stähler, S. C.**, Sigloch, K., Hosseini, K.,

Crawford, W. C., Barruol, G., Schmidt-Aursch, M. C., Tsekhmistrenko, M.,

Scholz, J.-R., Mazzullo, A., and Deen, M.:**Performance report of the****RHUM-RUM ocean bottom seismometer network around La Réunion, western****Indian Ocean**,*Adv. Geosci.*, 41, 43-63, doi:10.5194/adgeo-41-43-2016,

2016.The Lack of Equipartitioning in Global Body Wave Coda

Analysing seismograms of the deep Okhotsk earthquake, we can show that the late coda is dominated by waves traveling in great-circle direction. The coda is not equipartioned and cannot be easily used for correlation analysis.

Sens-Schönfelder, C., R. Snieder, and

**S. C. Stähler**(2015),**The Lack of Equipartitioning in Global Body Wave Coda**,*Geophys. Res. Lett.*, 42,doi:10.1002/2015GL065108.

Fully probabilistic seismic source inversion I - Efficient parametrization

This paper deals with the inverse problem of seismic point source inversion. It describes an efficient parametrization to invert for earthquake depth, moment tensor and source time function using

*Bayesian inference*with Malcolm Sambridge's*Neighbourhood Algorithm*.**Stähler, S. C.**and K. Sigloch (2014):**Fully probabilistic seismic source inversion – Part 1: Efficient parametrisation**,*Solid Earth,*5, 1055-1069**Instaseis: instant global seismograms based on a broadband waveform database**Instaseis is a Python library to calculate broadband seismograms for arbitrary source-receiver configurations, including finite faults and single forces from a stored AxiSEM wavefield.

van Driel, M., Krischer, L.,

**Stähler, S. C.**, Hosseini, K., and Nissen-Meyer, T. (2015).**Instaseis: instant global seismograms based on a broadband waveform database***Solid Earth*, 6, 701-717AxiSEM: broadband 3-D seismic wavefields in axisymmetric media

This is a release paper for the axially-symmetric spectral element solver AxiSEM. Use it to generate global seismograms for up to 1 Hz.

Nissen-Meyer, T., M. van Driel,

**S. C. Stähler**, K. Hosseini, S. Hempel, L. Auer, A. Colombi, and A. Fournier (2014):**AxiSEM: broadband 3-D seismic wavefields in axisymmetric media**,*Solid Earth*, 5, 425-445,Triplicated P-wave measurements for waveform tomography of the mantle transition zone

P-waves from distances between 1000 and 3000 km contain a lot of information about the upper mantle and the transition zone. We show a way to use them for finite-frequency tomography.

**Stähler, S. C**., K. Sigloch, and T. Nissen-Meyer (2012),**Triplicated P-wave measurements for waveform tomography of the mantle transition zone**,*Solid Earth*, 3(2), 339-354,Monitoring stress changes in a concrete bridge with coda wave interferometry

Coda waves contain information about a large volume around the source and receiver. We use that method to monitor stress changes in a bridge during construction.

**Stähler, S. C.**, E. Niederleithinger, and C. Sens-Schönfelder (2011),**Monitoring stress changes in a concrete bridge with coda wave interferometry**,*Journal of the Acoustical Society of America*, 129(4), 1945-1952,Blog

The latest from the lab and the field

Educational resources

Introductory seismology with animations

Seismic wavefield perturbed by plumes and slabs

This video shows the seismic wavefield of an earthquake in a mantle that contains a subducting slab on the left and an upwelling megaswell-structure on the right. The situation is comparable to Southern America on the left and Africa on the right with the earthquake happening in the Central Atlantic ocean at the mid-ocean ridge.

Note that the velocity anomalies are exaggerated to make the effect more prominent.

Seismic wavefield in the Jovian moon Europa

AxiSEM is able to model seismic wave propagation in terrestrial planets in general. One of the most fascinating objects in the solar system is Europa, with its abysmal ocean below a few kilometers of ice. The structure results in a wavefield that is completely different from what we see on Earth. Most of the wave energy is either contained inside the ice (especially SH-waves) or is reverberating inside the ocean.

Seismic wavefield in the Earth

This video shows the seismic wavefield in the Earth's mantle assuming the velocity depends only on depth.

Seismic wavefield perturbed by a megaswell-structure

This video shows a wavefield in a mantle that contains a megaswell.

Current collaborations

standing next to giants (without stepping on their toes)

Karin Sigloch

University of Oxford

My doctoral advisor and a great scientist.

Collaboration on finite-frequency tomography, especially on Northern America using triplicated P-waves and the Réunion hotspot.

Kasra Hosseini

University of Oxford

Kasra will be the first to use M.C. Kernel for a seismic tomography, based on his extensive P and Pdiff dataset

Mechita Schmidt-Aursch

Alfred-Wegener-Institut

Mechita runs the German national OBS pool DEPAS. We collaborate on estimating the noise level of the DEPAS' OBS and what to do about it.

Martin van Driel

ETH Zürich

Collaboration on the AxiSEM spectral element code and sensitivity kernels for seismic tomography.

Céline Hadziioannou

University of Hamburg

Earthquake-free seismology. Using seismic signals created from ocean waves, trucks or just anything for monitoring.

Steve Vance

Jet Propulsion Laboratory

Steve creates thermodynamically consistent interior models of icy moons in the outer solar system. Combined with AxiSEM, we can calculate their seismic response.

© 2016 Simon C. Stähler

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