A research project recently approved by the Swiss National Science Foundation aims to determine the risks posed by these rare events, what it takes to trigger lake tsunamis, how often they have occurred in the past, and the impact they create. As part of the project, scientists from ETH Zurich, the University of Bern and the University of Bremen's Centre for Marine Environmental Sciences (Marum) are planning to install nine ocean-bottom seismometers on the bed of Lake Lucerne. They will be the core equipment used to take seismic and geotechnical measurements of the lake sediments. Applications were also submitted to the Cantons of Lucerne, Nidwalden and Schwyz, but Lake Lucerne was chosen because of its location in a region of comparatively high seismic hazard and also because a lot is known about the lake bottom from previous research projects.

The plan is to place the measuring devices at various locations in the lake for a period of 22 months. The seismic data collected, combined with other measurement results, will be used to characterise the internal structure of slope instabilities, to better understand their slide mechanics and to model the generation and propagation of tsunami waves. Such a comprehensive investigation of hazard processes beneath the water surface is the first of its kind in Switzerland and its findings will help to improve the understanding of such processes around the world. The total cost of the project is CHF 2 million, much of which will be spent on the complex process of collecting the measurements.

Generally, accelerometers, measuring the acceleration of the ground motion, are used to register strong earthquakes. The ground motion they can record is limited in the low frequency range (slow motion) while GPS instruments are conversely limited in the high frequency range (rapid motion). Permanent GPS (GNSS) stations are covering the globe to serve as reference points for surveying and positioning. GPS instruments are therefore complementary in the way they record ground vibrations and their network is complementary in terms of spatial coverage.

To make use of these advantages, the aforementioned study is investigating what future improvements of GPS data processing will bring (see red area in the graphic). Recording strong earthquakes could be further optimized by increasing the sampling rate of GPS stations by a factor of two to five. GPS data is an added value to conventional accelerometric data for events of a magnitude 5.8 or greater within a radius of 10 km. Their integration into emergency tools such as ShakeMaps might therefore be of great value in countries with a high seismic hazard, like Japan.

Figure: Capability of GPS permanent stations to record strong earthquakes in real-time (blue) as a function of magnitude and distance from the fault rupture. What is currently doable after post processing (red) will be achieved in the future in real-time.

Clotaire Michel, Krisztina Kelevitz, Nicolas Houlié, Benjamin Edwards, Panagiotis Psimoulis, Zhenzhong Su, John Clinton, Domenico Giardini; The Potential of High‐Rate GPS for Strong Ground Motion Assessment. Bulletin of the Seismological Society of America ; 107 (4): 1849–1859. doi: https://doi.org/10.1785/0120160296

However, with only one seismometer this is a very challenging task. In contrast to a seismic network on earth with numerous stations, additional reference points that constrain the origin of the signals registered is missing. In preparation of the mission, scientists with experience in earthquake location and characterisation problems are invited to share their knowledge by participating in a blind test.

Based on a synthetic dataset, we aim to improve the planned single station location methods to be used in the routine analysis of the martian dataset. The waveforms provided in the blind test mimic both the streams of data that will be available from InSight, as well as the expected level of tectonic and impact seismicity and the noise conditions on Mars. The test is 'blind' in the sense that the actual event catalogue is not provided to any participants, and the structural model used to generate the seismograms has been selected from a suite of 14 candidate models. In course of the blind test, we hope to learn from the methodologies proposed by the community. The blind test is described in detail in a recent publication in SRL (Clinton et al., 2017, Preparing for InSight: an invitation to participate in a blind test for Martian seismicity, Seism. Res. Letters, doi: 10.1785/0220170094).

The test officially opened on 1 August 2017 and registration will close on 1 October 2017. All participants must provide their event catalogues by 1 February 2018.  A website where interested parties can register and access seismic waveforms is available at http://blindtest.mars.ethz.ch.

All groups who contribute a catalogue to the blind test will be invited to be co-authors on a paper summarising methods and performance with respect to the true event catalogue that will then be released.

We encourage scientists and students, in teams of any size, to investigate the blind test dataset and we look forward to your participation!