Seismic monitoring: why and how Prof. Stefan Wiemer, Swiss Seismological Service

Transcription

1 Seismic monitoring: why and how Prof. Stefan Wiemer, Swiss Seismological Service

2 You want Energy. Why monitor earthquakes? It may be legally required. It will help you to distinguish natural seismicity from induced/triggered ones It will help to build/maintain public acceptance It will help you to operate controls and mitigation systems ( traffic lights ) It will inform you about processes in you reservoir and may help to increase productivity by balancing safety concerns and economical output.

3 Natural or Induced: Nov Pohang M5.5 earthquake

4 But what kind of monitoring do I need? It depends! Monitoring requirements vary between nothing at all to a local monitoring network with advanced traffic lights system attached. And costs likewise vary also!

5 Step 1 in Risk Governance: Rapid screening We often were faced with the question what kind of risk governance are needed for a specific project. And we wanted to be more objective, reproducible. So we write a paper Geothermal Risk of Induced seismicity Diagnosis (GRID),

6 GRID Based on a set of initial screening parameters, we propose tailor made risk governance workflows for different project categories. This is of course subjective and not a replacement for a subsequent risk study. GRID is best done independently by all stakeholders before the project starts and then discussed.

7 GRID Criteria

8 GRID Examples

9 Holistic concept of risk governance & community resilience From risk analysis Data analysis & statistics Physical process understanding Risk modeling To risk management & governance Risk grading / stress tests Traffic-light systems Communication with industry, regulators & public.

10 And into good practise recommodations Practice-Guide-for-Managing-Induced-Seismicity-in-Deep-Geothermal-Energy-Projects-in-Switzerland_v1.0.pdf

11 Other good frameworks exist...

12 Monitor: How? Define your targets in location accuracy, magnitude of completeness, speed, duration of the operation. Plan ahead. A prior network optimization pays off many times! Team up: There is often stations and competence nearby. Invest in finding good, quiet sites, it is worth it! Consider borehole sites. Gutenberg Richter helps a lot! Don t be scared of too many micro-earthquakes.

13 SDSNet-Stationen (Stand ) proposed locations for the relevant stations we plan to build for SDSNet upgrade (red). the locations of the now existing 3 CERN stations (green) the locations of existing FR stations (blue)

14 Invest in processing Modern seismological tools can be so much more powerful to resolve structures and processes

15 Get to know your faults and earthquakes better Understanding the seismo-tectonic context and knowing your faults is critically important. Diehl et al., 2017

16 From micro-seismicity to process understanding Diehl et al., 2017

17 Basel: Renewed increase? In the following years after 2006: decay of seismicity Marcus Herrmann Induced Seismicity in Basel AGU Fall Meeting, SED catalog Swiss Seismological Service (only surface stations) 2.GEL catalog Borehole network operator (incl. deep borehole stations) Completeness-level of SED catalog Completeness-level of GEL catalog

18 Renewed increase? Marcus Herrmann Induced Seismicity in Basel AGU Fall Meeting, In 2012, increase of seismicity, stop of borehole network 1.SED catalog 2.GEL catalog Swiss Seismological Borehole network Service operator (only surface stations) (incl. deep borehole stations) Completeness-level of SED

19 Renewed increase? Marcus Herrmann Induced Seismicity in Basel AGU Fall Meeting, In 2012, increase of seismicity, stop of borehole network Borehole closed Completeness-level of SED

20 Renewed increase? Marcus Herrmann Induced Seismicity in Basel AGU Fall Meeting, From 2011 onwards: pressure increase Borehole closed Completeness-level of SED

21 Template Event Locations templates representation of the seismic cloud Locations: [Dyer et al. 2010; Deichmann e Scanning 11 years necessary to run our detector on a supercomputer (parallel) Marcus Herrmann Induced Seismicity in Basel AGU Fall Meeting,

22 Searching for more Marcus Herrmann Induced Seismicity in Basel AGU Fall Meeting, Template Matching (= matched filter analysis) Scanning seismic recordings for similar earthquakes / waveforms (using the ones we already the deepest borehole station (OTER2) (most sensitive to reservoir earthquakes) sediments OTER2 ~1.5km granite seismic cloud

23 Hermann et al., 2018

24 Statistical Analysis Time-series a-value + b-value = aily probability of M3+ time-varying hazard analysis Same hazard level as late (postinjection)

25 Down, and up, and down again

26 Down, and up, and down again

27 Zoback, 2012, Monitoring drives Traffic light systems Classical Traffic light systems are useful But also have limitations source: Bosman et al. (2016)

28 Moving on to Adaptive, data -driven Traffic Light Systems (ATLS) ATLS are dynamically updated, forward-looking and fully probabilistic models that forecast the future seismicity and reservoir evolution based on a range of relevant key parameters (eq., K P, T, ). Consider also low probability-high consequence events. Robustness through ensemble forecasting.

29 Adaptive Traffic Light Systems Grigoli et al., Rev. of Geoph., 2017

30 Thank you!

31 Liability claim The European Union and its Innovation and Networks Executive Agency (INEA) are not responsible for any use that may be made of the information any communication activity contains. The content of this publication does not reflect the official opinion of the European Union. Responsibility for the information and views expressed in the therein lies entirely with the author(s). DESTRESS is co-funded by National Research Foundation of Korea (NRF) Korea Institute for Advancement of Technology (KIAT) Swiss State Secretariat for Education, Research and Innovation (SERI)