Characterization of the co-seismic slip field for large earthquakes

Focused studies on large earthquakes have highlighted that ruptures on generating faults are strongly heterogeneous. The main aim of this thesis is to explore characteristic patterns of the slip distribution of large earthquakes, by using the finite-fault models (FFM) obtained in the last 25 years. A result of this thesis is the computation of regression laws linking focal parameters with magnitude. Particular attention was devoted to the aspect ratio (A.R.), defined as the ratio between fault length and width. FFMs have been partitioned in 3 A.R. classes and for each class, the position of the hypocentre, of the maximum slip and their mutual relation were investigated. To favour inter-comparison, normalised images of on-fault seismic slip were produced on geometries typical of each A.R. class with the goal of finding possible regularities of the slip distribution shapes. In this thesis, the shape of the single-asperity FFMs has been fitted by means of 2D Gaussian distributions. To the knowledge of the author, this thesis is the first example of a systematic study of finite-fault solutions to identify the main pattern of the on-fault co-seismic slip of large earthquakes. One of the foreseen applications is related to tsunamigenesis. It is known that tsunamis are mainly determined by the vertical displacement of the seafloor induced by large submarine earthquakes. In this thesis, the near-source vertical-displacement fields produced by the FFM (assumed as the real one), by a homogeneous fault model, by a depth-heterogeneous fault model and by two distinct 2D Gaussian distribution fault models were computed and compared for all single-asperity earthquakes. The main finding is that 2D Gaussian distributions give the least misfit fields and are therefore the most adequate for tsunami generation modelling

On the implementation of faults in finite-element glacial isostatic adjustment models

postprin

Crustal Deformation and Fault Strength of the Sulawesi Subduction Zone

This paper investigates the seismicity and rheology of the North-Sulawesi subduction zone. Body-wave modeling is used to estimate focal mechanisms and centroid depths of moderate magnitude (M5–M6.5) earthquakes on the North Sulawesi megathrust and surrounding region. The slip vectors of megathrust earthquakes radiate outward from Sulawesi, indicating motion that is incompatible with the relative motion of two rigid plates. Instead, the observed deformation implies lateral spreading of high topography, controlled by gravitational potential energy contrasts. This finding suggests that the observed deformation of Sulawesi results from stresses transmitted through the lithosphere, rather than basal tractions due to circulation in the mantle. Our modeling of the force balance on the megathrust shows that the subduction megathrust is weak, with an average shear stress of ∼13 MPa and an effective coefficient of friction of 0.03. Elsewhere in Sulawesi, slip vectors of other earthquakes suggest similar potential-energy-driven deformation is present, but at significantly slower rates. Our results show the importance of lateral rheology contrasts in determining deformation rate, and hence seismic hazard, in response to a given driving force.Newton Institutional Links Leverhulme Fellowshi

Late Pleistocene‐Holocene Slip Rates in the Northwestern Zagros Mountains (Kurdistan Region of Iraq) Derived From Luminescence Dating of River Terraces and Structural Modeling

Abstract A significant amount of the ongoing shortening between the Eurasian and Arabian plates is accommodated within the Zagros Fold‐Thrust Belt. However, the spatial and temporal distribution of active shortening within the belt, especially in its NW part, is not yet well constrained. We determined depositional ages of uplifted river terraces crossing the belt along the Greater Zab River using luminescence dating. Kinematic modeling of the fault‐related fold belt was then used to calculate long‐term slip rates during the Late Pleistocene to Holocene. Our results provide new insight into the rates of active faulting and folding in the area. The Zagros Mountain Front Fault accommodates about 1.46 ± 0.60 mm a −1 of slip, while a more external basement fault further to the SW accommodates less than 0.41 ± 0.16 mm a −1 . Horizontal slip rates related to detachment folding of two anticlines within the Zagros Foothills are 0.40 ± 0.10 and 1.24 ± 0.36 mm a −1 . Basement thrusting and thickening of the crust are restricted to the NE part of the Zagros belt. This is also reflected in the regional topography and in the distribution of uplifted terraces. In the southwestern part, the deformation is limited mainly to folding and thrusting of the sedimentary cover above a Triassic basal detachment. In the NE, deformation is associated with slip on basement thrusts. Our study sheds light on the distribution of shortening in the Zagros Mountains and helps to understand the regional tectonic system. Our results may be the foundation for a better seismic hazard assessment of the entire area.Plain Language Summary In active mountain belts, river terraces found above the present‐day river level can be indicative of differences in uplift rates due to the thickening, faulting, and folding processes in the Earth's crust. These processes, driven by the motion of tectonic plates, are responsible for the formation of mountain belts. Here, we took sediment samples from uplifted river terraces along the Greater Zab River that crosses the Zagros Mountains in the Kurdistan Region of Iraq. We determined their deposition age using luminescence dating. From their age and elevation, we calculated uplift rates. We built a geometrical model of the fault zones in the area and determined how fast the slip occurs on these faults based on the uplift rates. Our results indicate that there were less than two millimeter per year of slip on these faults on average during the last 60 thousand years. This motion is a result of the convergence between the Arabian and Eurasian plates. With studies like this we can measure how fast fault blocks move, even if they were not associated with large earthquakes in the recent past. This approach helps to better assess the potential earthquake hazard in the area under investigation.Key Points We estimated fault slip rates in the NW Zagros Mountains by luminescence dating of river terraces and structural modeling There is c. 1.46 mm a −1 slip on the Mountain Front Fault and c. 1.64 mm a −1 slip from detachment folding in the NE part of the Foothill Zone Crustal thickening and basement thrusting occur in the NE parts of the Foothill Zone and only cover deformation occur in the SW part

Development of Response Spectra for the HBPP ISFSI

Calc Number: GEO.HBIP.02.04 Revision:

Development of Response Spectra for the HBPP ISFSI

Calc Number: GEO.HBIP.02.04 Revision:

3C Seismic Interferometry at the Polymetallic Kylylahti Deposit, Outokumpu District, Finland

Non peer reviewe

New digital learning materials for teaching in geosciences

Non peer reviewe

Seismic mineral exploration at different scales in the Outokumpu Ore District, Eastern Finland

Non peer reviewe