WP 4.2 Analysis, inversion and estimation of strong ground motion data from extended-earthquake fault models  of the two June 2000 Iceland events

Start date or starting event:


Lead contractor:


Participants:                                                UNIVTS-DST, IMOR, UI


Objectives: 1)  Inversion of strong ground motion (accelerograms) data related to the two June 2000 events in Iceland using particular station distributions to retrieve the slip distribution on the fault. 2) Analysis of the reliability of the above inversions using particular station distributions and different physical constraints. 3) Estimation of the strong ground motion due to the June 2000 events in localities with no instrumental recording and assessment of their damage potential, in strong collaboration with Icelandic engineers.


Methodology / work description:

1) Methods of inversion of strong ground motion data and analysis of  the reliability of the solutions obtained:

During the course of a previous EC funded project (SGME) the method of inversion of seismic data was further developed and tested. It has been shown that simple least squares solutions are very non-unique and lead to physically unrealistic results, such as adjacent grids on the fault having slip in opposite directions. Constraints, based on the physics of the problem, were introduced in order to reduce the non-uniqueness. The most important constraint was that of non-negativity of the slip rate on the fault. With this, physically reasonable solutions are obtained. Additional constraints such as requiring the scalar seismic moment of the solution to be equal to some prescribed value, say that obtained from the CMT solution or from GPS studies, limiting the maximum fault rupture speed and/or the maximum fault slip speed, etc. were also used. We intend, in the framework of this project, to use and further refine these tested programs, in particular to assess the robustness of the inverted solutions and how the robustness depends on the choice of the physical constraints imposed. The programs will be applied to study in detail the energy release on the fault during the two June 2000 earthquakes that occurred in the south of Iceland. We would also like to test and use Empirical Greens Functions (EGF) method to invert the mainshock strong motion data and compare the results with those obtained using theoretical Greens functions in a 1-D anelastic medium.

2) Estimation of strong ground motion for seismic hazard reduction purposes in Iceland:

 On the basis of the obtained fault model we plan to estimate the strong ground motion (complete time series records) in localities where the June 2000 events have not been recorded. On the basis of other models of earthquake rupturing that could take place in Iceland in the future both on the same faults or on adjacent ones (indications to be provided by active tectonic studies in the region)  more estimates will be made. This will provide engineers with design time series to be used in the seismic hazard assessment of particular structures and help them in the understanding the observed damage in other localities with no observed ground motion record. In strong connection with the engineering community the damaging potential of such records will be estimated. The relation of damaging potential upon the characteristics of the estimated ground motion and upon the causative scenario event will lead to the worst scenario case. Should the local conditions require it and with certain approximations, we will also estimate the ground motion in 2D anelastic media for some important localities.



Deliverables including cost of deliverable as percentage of total cost of the proposed project:


Preliminary slip model of rupture on the fault of the first earthquake.

M8    Re  PU  0,3%


Best slip model of rupture on the fault of the first earthquake.

M12  Re  PU  0,4%


Inversion for slip related to the second earthquake.

M14  Re  PU  0,4%


Estimated acceleration field in selected localities for first event.

M14   Re  PU  0,4%


Preliminary slip model of rupture on the fault of the second event.

M18   Re  PU  0,4%


Best slip model of rupture on the fault of the second earthquake.

M20   Re  PU  0,5%


Estimated acceleration field in selected localities  for a future event in SISZ and assessment of their damage potential.

M24   Re  PU  0,9%



Milestones: Delivery of the above items at the date indicated.