Natural Time and Nowcasting Induced Seismicity at the Groningen Gas Field in the Netherlands

Molly Luginbuhl, Donald L. Turcotte, & John B. Rundle

Published August 11, 2017, SCEC Contribution #7494, 2017 SCEC Annual Meeting Poster #002

The area surrounding the Groningen natural gas field in the Netherlands has recently seen a significant increase in seismicity. How to handle this induced seismicity has become a controversial topic for many. The gas field provides energy for the majority of the country; however, for a minority of Dutch citizens who live nearby, the seismicity induced by the gas field is a cause for major concern. Since the early 2000’s, the region has seen an increase in both number and magnitude of events, the largest of which was a magnitude 3.6 in 2012. This is concerning because earthquakes of this size and smaller easily cause infrastructural damage to older houses and farms built with single brick walls, which are common in much of Europe. Nowcasting is a new method of statistically classifying seismicity and seismic risk. We apply this method to the induced seismicity at the natural gas fields in Groningen, Netherlands. Nowcasting utilizes the catalogs of seismicity in the region. Two earthquake magnitudes are selected, one large say M > 2.5, and one small say M > 1.0. The method utilizes the number of small earthquakes that occur between pairs of large earthquakes. The cumulative probability distribution of these values is obtained. The earthquake potential score (EPS) is defined by the number of small earthquakes that have occurred since the last large earthquake, the point where this number falls on the cumulative probability distribution of interevent counts defines the EPS. A major advantage of nowcasting is that it utilizes “natural time”, earthquake counts, between events rather than clock time. Thus, it is not necessary to decluster aftershocks and the results are applicable if the level of induced seismicity varies in time, which it does here. The application of natural time to the accumulation of the seismic hazard depends on the applicability of Gutenberg-Richter (GR) scaling. The increasing number of small earthquakes that occur after a large earthquake can be scaled to give the hazard of a large earthquake occurring. To illustrate our approach, we utilize the number of M > 1.0 earthquakes in Groningen to nowcast the number of M > 2.5 earthquakes in Groningen. The applicability of the scaling is illustrated during the rapid build up of seismicity between 2004 and 2016.

Key Words
Natural Time, Nowcasting, Induced Seismicity, Groningen

Citation
Luginbuhl, M., Turcotte, D. L., & Rundle, J. B. (2017, 08). Natural Time and Nowcasting Induced Seismicity at the Groningen Gas Field in the Netherlands. Poster Presentation at 2017 SCEC Annual Meeting.

Related Projects & Working Groups
Earthquake Forecasting and Predictability (EFP)