From Top to Bottom- Seismicity, Motion Patterns & Stress Distribution in the Alpine Crust.

Funding period: 2017-2020 (the DFG has recently granted the continuation until 2023)
PI's: Jörn Kummerow (FUBerlin), Simone Cesca (GFZ Potsdam), Joachim Wassermann (LMU München) & Thomas Plenefisch (BGR Hannover)

Summary

This project is part of the DFG priority programme MB-4D. The aim of our project is to investigate the processes which control the seismicity of the Alps. We hypothesize that patterns of stress and motion can be quantified from the seismicity which is observed with unprecedented resolution by Alparray. A major challenge are the detection and analysis of weak seismic events which are of prime importance for establishing the link between near-surface and deep crustal processes. We face this by a consistent analyis of local-scale data recorded by the dense seismic network SWATH-D at the transition between Eastern and Southern Alps, usinng modern waveform-based seismological techniques for event detection and location. In close cooperation with MB-4D projects from other disciplines (more details here), our project will enable us to derive spatial and eventually temporal patterns of motion, deformation and stresses and finally contribute to an improved understanding of the Alpine mountain building process.

Anatomy of a Subduction Zone from Ocean Mantle to Crust: Seismicity and Seismic Structure in Northern Chile.

Funding period: 2015-2019
PI's: Jörn Kummerow (FUBerlin), Bernd Schurr (GFZ Potsdam) & Serge A. Shapiro (FUBerlin)

Summary

We investigate subduction-related seismic structures, including the fine-scale structure of the megathrust shear zone and underlying oceanic plate, and of earthquake sources in the northern Chile forearc by employing a suite of innovative methods of seismicity processing, imaging and interpretation. We will exploit the specific situation, where an extraordinarily high rate of seismicity has been recorded for almost ten years on a large number of seismic stations, including the permanent IPOC network and several temporary networks. Northern Chile, in particular the recently installed MEJIPE network on the Mejillones peninsula, also offers a rare chance to monitor at least a part of the seismogenic zone onshore. We therefore expect to image the structural and seismic architecture of this subduction zone at highest possible resolution.
An important component of the project will be the detailed study of seismicity and related physical processes in the deepest, upper ocean mantle layer of the newly confirmed shallow triple seismic zone in northern Chile. Eventually this will contribute to advance the understanding of intermediate depth earthquakes in general.

Related publications

Sippl, C., B. Schurr, G. Asch, and J. Kummerow (2018), Seismicity structure of the Northern Chile forearc from >100,000 double‐difference relocated hypocenters. Journal of Geophysical Research,123, doi.org/10.1002/2017JB015384

Bloch, W., B. Schurr, J. Kummerow, P. Salazar, and S. A. Shapiro (2018), From Slab Coupling to Slab Pull: Stress Segmentation in the Subducting Nazca Plate. Geophysical Research Letters, doi.org/10.1029/2018GL078793

Bloch, W., T. John, J. Kummerow, P. Salazar, O. S. Krüger, and S. A. Shapiro (2018), Watching Dehydration: Seismic Indication for Transient Fluid Pathways in the Oceanic Mantle of the Subducting Nazca Slab. Geochemistry, Geophysics, Geosystems, doi.org/10.1029/2018GC007703

Salazar, P., J. Kummerow, P. Wigger, S. A. Shapiro, and G. Asch (2017), State of stress and crustal fluid migration related to west-dipping structures in the slab-forearc system in the northern Chilean subduction zone. Geophysical Journal International, 208(3), 1403-1413, doi.org/10.1093/gji/ggw463

Bloch, W., J. Kummerow, P. Salazar, P. Wigger, and S. A. Shapiro (2014), High-resolution image of the North Chilean subduction zone: seismicity, reflectivity and fluids. Geophysical Journal International, 197(3), 1744-1749, doi.org/10.1093/gji/ggu084

Disentangling roles of stress, pore pressure and shaking from wavefields recorded
during the 2014 Northern Chile earthquake sequence — WAVEFIELDS.

Funding period: 2015-2019
PI's: Jörn Kummerow (FUBerlin), Dr. Christoph Sens-Schönfelder (GFZ Potsdam), Serge A. Shapiro (FUBerlin) & Frederik Tilmann (FUBerlin, GFZ Potsdam)

Summary

This project aims at quantifying and understanding the structural dynamics within the crust leading to, during and after a great megathrust earthquake. This includes the evolution of stress in the lithosphere and identifying signatures of possible fluid migration at depth. We will exploit the dataset acquired during the 2014 M W 8.1 Iquique earthquake sequence, which is distinguished from most other great subduction earthquakes in the first place by its rich foreshock sequence but also the continuity of monitoring by the IPOC network.

Related publications

Folesky, J., J. Kummerow and S. A. Shapiro (2018), Patterns of rupture directivity of subduction zone earthquakes in northern Chile . Journal of Geophysical Research,123, doi.org/10.1029/2018JB016331

Folesky, J., J. Kummerow, G. Asch, B. Schurr, Ch. Sippl, F. Tilmann, S. A. Shapiro (2018), Estimating Rupture Directions from Local Earthquake Data Using the IPOC Observatory in Northern Chile. Seismological Research Letters ; 89 (2A): 495–502, doi.org/10.1785/0220170202

Rupture processes and magnitude statistics of induced earthquakes and aftershocks:
A detailed view from deep South African gold mines.

Funding period: 2017-2019
PI's: Serge A. Shapiro (FUBerlin) & Jörn Kummerow (FUBerlin)

Summary

Despite our general understanding of earthquake processes, it is still not fully understood how earthquakes ruptures nucleate and propagate and why they stop. Furthermore, the controlling factors of the frequency and the size of earthquake are subject of ongoing research. In our proposal, we aim to address these questions with a comprehensive study of seismicity in deep South African gold mines. Here, we find the unique situation that the seismicity consists of both mining-induced earthquakes and triggered aftershocks. We hypothesize that the finiteness and geometry of the volume of stress perturbation, either by mining activity or by a main shock, controls the nucleation and propagation of ruptures and influences the frequency-magnitude distribution. To test our hypothesis, we will apply novel approaches to the seismicity from the deep mines which involve both waveform-based and probabilistic methods. These methods were recently elaborated and successfully applied to fluid injection induced earthquakes and include rupture propagation imaging, rupture directivity analysis, and studies of the scaling of the magnitude statistics. In this proposal, we want to test the applicability of these approaches to the seismicity in deep South African mines, which also occurs in a finite volume, which will contribute to a better understanding of seismogenic processes and, in particular, to an improved assessment and the mitigation of seismic hazard in mining environment.