Application of full-waveform event location and moment-tensor inversion for Groningen induced seismicity

2018 ◽  
Vol 37 (2) ◽  
pp. 92-99 ◽  
Author(s):  
Chris Willacy ◽  
Ewoud van Dedem ◽  
Sara Minisini ◽  
Junlun Li ◽  
Jan Willem Blokland ◽  
...  
Keyword(s):  
Induced Seismicity ◽  
Moment Tensor ◽  
Moment Tensor Inversion ◽  
Full Waveform ◽  
Event Location

scholarly journals Full-waveform event location and moment tensor inversion for induced seismicity

Geophysics ◽  
2019 ◽  
Vol 84 (2) ◽  
pp. KS39-KS57 ◽  
Author(s):  
Chris Willacy ◽  
Ewoud van Dedem ◽  
Sara Minisini ◽  
Junlun Li ◽  
Jan-Willem Blokland ◽  
...  
Keyword(s):  
Induced Seismicity ◽  
Moment Tensor ◽  
Focal Mechanisms ◽  
Moment Tensor Inversion ◽  
Earthquake Activity ◽  
Lower Velocity ◽  
Full Waveform ◽  
Stress Changes ◽  
Event Location ◽  
Location Methods

Locating microearthquake events below complex heterogeneous overburden requires robust location methodologies that can honor multipathing in the seismic wavefield. We have developed two full-waveform event location methods that form a complementary solution for locating earthquakes and simultaneously deriving focal mechanisms via moment tensor inversion. The methods are based on the application of 3D elastic wavefield modeling, which is used to generate waveforms and extract wavefield attributes, for comparison to the observed field data. Events are located and focal mechanisms are derived via a multiparameter inversion, which minimizes the differences between synthetic and observed data. The results have been applied to the induced seismicity observed within the giant Groningen gas field, onshore Netherlands, where recorded earthquakes are triggered by stress changes, induced in the reservoir through pressure depletion. Locating events below the field is compounded by the presence of strong guided waves, which are trapped in the lower velocity reservoir interval. This complex multivalued wavefield is problematic for traditional event location methods, which assume a single traveltime arrival. We overcome this limitation by using all event arrivals in a wave-based solution to improve the accuracy of locating earthquakes and overcome the ambiguity of solving for location and the focal mechanism simultaneously. The event location methods have been applied to shallow and deep monitoring networks, and 150 events have been located with high accuracy. The interpretation of the earthquake activity indicates that the events studied originate from the movement of larger graben bounding faults, which are oriented in a north-northwest–south-southeast direction.

Automating event location monitoring for induced seismicity

2020 ◽  
Vol 39 (7) ◽  
pp. 505-512
Author(s):  
Christopher Willacy ◽  
Jan-Willem Blokland ◽  
Ewoud van Dedem
Keyword(s):  
Induced Seismicity ◽  
Moment Tensor ◽  
Moment Tensor Inversion ◽  
Computer Hardware ◽  
Gas Field ◽  
Elastic Event ◽  
Event Location ◽  
Double Couple ◽  
Couple Motion ◽  
Hazard Level

Permanent reservoir monitoring is important for cases of induced seismicity in which there may be a risk to people or to the environment. In such cases, accurately locating microearthquakes and assessing their hazard level can help keep production at safe levels. The process can benefit greatly from the use of automation. With the shift toward full-waveform microearthquake location algorithms and workflows, greater accuracy and information can be retrieved compared to that offered by traditional traveltime estimation techniques, but the complexity of these workflows and run-time costs can be higher. Results are presented from an automatic elastic event location and moment tensor inversion workflow that has been highly parallelized on clustered computer hardware. Run times that previously took up to several days to complete using a manually intensive execution of the workflow now can be achieved in approximately 1 hour. Some 180 events recorded at the Groningen gas field and ranging in magnitude from 0.1 to 3.4 MW (ML) have been located and analyzed with the automatic workflow. The results indicate equivalent location accuracy when compared to the manually intensive workflow execution. However, larger errors are noted in the depth positions of some events and in the range and nature of the focal mechanism, as derived from moment tensor inversion. High grading of the manual and automatic results has been performed and used to study the geomechanical behavior of the microearthquakes in the Groningen region, which exhibit mainly dip-slip, double-couple motion, in areas of previous production activity.

scholarly journals Automated full moment tensor inversion of coal mining-induced seismicity

2013 ◽  
Vol 195 (2) ◽  
pp. 1267-1281 ◽  
Author(s):  
Ali Tolga Sen ◽  
Simone Cesca ◽  
Monika Bischoff ◽  
Thomas Meier ◽  
Torsten Dahm
Keyword(s):  
Coal Mining ◽  
Induced Seismicity ◽  
Moment Tensor ◽  
Moment Tensor Inversion ◽  
Mining Induced Seismicity ◽  
Full Moment Tensor

Probabilistic Moment Tensor Inversion for Hydrocarbon-Induced Seismicity in the Groningen Gas Field, the Netherlands, Part 2: Application

2020 ◽  
Vol 110 (5) ◽  
pp. 2112-2123 ◽  
Author(s):  
Bernard Dost ◽  
Annemijn van Stiphout ◽  
Daniela Kühn ◽  
Marloes Kortekaas ◽  
Elmer Ruigrok ◽  
...  
Keyword(s):  
Induced Seismicity ◽  
Moment Tensor ◽  
Moment Tensor Inversion ◽  
Gas Field ◽  
Double Couple ◽  
Recent Developments ◽  
Inversion Procedure ◽  
Seismic Sections ◽  
The Moment ◽  
Groningen Gas Field

ABSTRACT Recent developments in the densification of the seismic network covering the Groningen gas field allow a more detailed study of the connection between induced seismicity and reactivated faults around the gas reservoir at 3 km depth. With the reduction of the average station distance from 20 km to 4–5 km, a probabilistic full-waveform moment tensor inversion procedure could be applied, resulting in both improved hypocenter location accuracy and full moment tensor solutions for events of M≥2.0 recorded in the period 2016–2019. Hypocenter locations as output from the moment tensor inversion are compared to locations from the application of other methods and are found similar within 250 m distance. Moment tensor results show that the double-couple (DC) solutions are in accordance with the known structure, namely normal faulting along 50°–70° dipping faults. Comparison with reprocessed 3D seismic sections, extended to a depth of 6–7 km, demonstrate that (a) most events occur along faults with a small throw and (b) reactivated faults in the reservoir often continue downward in the Carboniferous underburden. From non-DC contributions, the isotropic (ISO) component is dominant and shows consistent negative values, which is expected in a compacting medium. There is some indication that events connected to faults with a large throw (>70  m) exhibit the largest ISO component (40%–50%).

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