Characterisation of ground motion recording stations in the Groningen gas field
J Seismol
Characterisation of ground motion recording stations in the Groningen gas field
Rik Noorlandt 0 1 2 3 4 5 6
Pauline P. Kruiver 0 1 2 3 4 5 6
Marco P. E. de Kleine 0 1 2 3 4 5 6
Marios Karaoulis 0 1 2 3 4 5 6
Ger de Lange 0 1 2 3 4 5 6
Antonio Di Matteo 0 1 2 3 4 5 6
Julius von Ketelhodt 0 1 2 3 4 5 6
Elmer Ruigrok 0 1 2 3 4 5 6
Benjamin Edwards 0 1 2 3 4 5 6
Adrian Rodriguez-Marek 0 1 2 3 4 5 6
Julian J. Bommer 0 1 2 3 4 5 6
Jan van Elk 0 1 2 3 4 5 6
Dirk Doornhof 0 1 2 3 4 5 6
0 J. von Ketelhodt Geotomographie GmbH Germany, now at School of Geosciences, University of the Witwatersrand Johannesburg , WITS 2050 , South Africa
1 A. Di Matteo Shell Global Solutions International B.V , Kessler Park 1, 2288 GS Rijswijk , The Netherlands
2 R. Noorlandt
3 J. J. Bommer Civil & Environmental Engineering, Imperial College London , London SW7 2AZ , UK
4 A. Rodriguez-Marek Charles E Via, Jr., Department of Civil and Environmental Engineering, Virginia Tech , Blacksburg, VA 24061 , USA
5 B. Edwards Department of Earth, Ocean and Ecological Sciences, University of Liverpool , Liverpool L69 3GP , UK
6 E. Ruigrok Royal Netherlands Meteorological Institute (KNMI) , Utrechtseweg 297, 3731 GA De Bilt , The Netherlands
The seismic hazard and risk analysis for the onshore Groningen gas field requires information about local soil properties, in particular shear-wave velocity (VS). A fieldwork campaign was conducted at 18 surface accelerograph stations of the monitoring network. The subsurface in the region consists of unconsolidated sediments and is heterogeneous in composition and properties. A range of different methods was applied to acquire in situ VS values to a target depth of at least 30 m. The techniques include seismic cone penetration tests (SCPT) with varying source offsets, multichannel analysis of surface waves (MASW) on Rayleigh waves with different processing approaches, microtremor array, cross-hole tomography and suspension P-S logging. The offset SCPT, cross-hole tomography and common midpoint cross-correlation (CMPcc) processing of MASW data all revealed lateral variations on length scales of several to tens of metres in this geological setting. SCPTs resulted in very detailed VS profiles with depth, but represent point measurements in a heterogeneous environment. The MASW results represent VS information on a larger spatial scale and smooth some of the heterogeneity encountered at the sites. The combination of MASW and SCPT proved to be a powerful and cost-effective approach in determining representative VS profiles at the accelerograph station sites. The measured VS profiles correspond well with the modelled profiles and they significantly enhance the ground motion model derivation. The similarity between the theoretical transfer function from the VS profile and the observed amplification from vertical array stations is also excellent.
1 Introduction
Induced earthquakes due to gas production in the
Groningen field in the northern Netherlands has prompted
the development of seismic hazard and loss estimation
models in order to allow risk-informed decision-making
with regard to mitigation options. A key element of the
seismic hazard and risk models for the Groningen field
is a ground motion prediction model to estimate surface
motions due to each possible earthquake scenario. The
ground motion model for the Groningen field is
comprised of predictive equations for spectral accelerations
and peak ground velocity at a reference rock horizon
(located at about 800 m depth) and non-linear
frequency-dependent amplification functions reflecting the
dynamic response of the overlying soil layers
(Bommer
et al., 2017)
.
The ground motion model derivation has benefited
from a database of recordings of ground motions
obtained from accelerograph and borehole geophone
networks installed in the Groningen field. The location of
the stations is shown in Fig. 1. The first stage of the
model building process is to deconvolve the recorded
surface motions to the reference rock horizon. The
uncertainty in this process is greatly reduced by the
accurate characterisation of dynamic properties of the soil
column, particularly in the uppermost tens of metres that
exert the strongest influence on the site response.
Although an excellent velocity model of the Groningen
field has been constructed using measurements at depths
from below about 50 m, the near-surface portion of the
profiles are inferred from lithological profiles with
shear-wave velocities (VS) assigned based on available
seismic CPT measurements
(Kruiver et al., 2017a)
. To
refine the profiles at the locations of the ground motion
recording stations, in situ VS measurements were made
using a variety of borehole and non-invasive techniques.
Challenges encountered in this work include the fact
that in several cases it was not possible to perform the
measurements in very close proximity to the location of
the recording stations. The paper describes how these (...truncated)