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triggering

EPSL paper on slow earthquake in the Sea of Marmara

We recently published a paper in Earth and Planetary Science Letters entitled “Slow strain release along the eastern Marmara region offshore Istanbul in conjunction with enhanced local seismic moment release”.

The paper was quite widely commented in a GFZ press release, as well as in the Science Daily and Phys.org.

Full reference:

Martínez-Garzón, P., M. Bohnhoff, D. Mencin, G. Kwiatek, G. Dresen, K. Hodgkinson, M. Nurlu, F. T. Kadirioglu, and R. F. Kartal (2019). Slow strain release along the eastern Marmara region offshore Istanbul in conjunction with enhanced local seismic moment release, Earth and Planetary Science Letters 510, 209–218, DOI: 10.1016/j.epsl.2019.01.001.

Abstract:

We analyze a large transient strainmeter signal recorded at 62.5 m depth along the southern shore of the eastern Sea of Marmara region in northwestern Turkey. This region represents a passage of stress transfer from the Izmit rupture to the Marmara seismic gap. The strain signal was recorded at the Esenkoy site by one of the ICDP-GONAF (International Continental Drilling Programme – Geophysical Observatory at the North Anatolian Fault) strainmeters on the Armutlu peninsula with a maximum amplitude of 5 microstrain and lasting about 50 days. The onset of the strain signal coincided with the origin time of a MW 4.4 earthquake offshore Yalova, which occurred as part of a seismic sequence including eight MW ≥3.5 earthquakes. The MW 4.4 event occurred at a distance of about 30 km from Esenkoy on June 25th 2016 representing the largest earthquake in this region since 2008. Before the event, the maximum horizontal strain was subparallel to the regional maximum horizontal stress derived from stress inversion of local seismicity. During the strain transient, we observe a clockwise rotation in the local horizontal strain field of about 20°. The strain signal does not correlate with known environmental parameters such as annual changes of sea level, rainfall or temperature. The strain signal could indicate local slow slip on the Cinarcik fault and thus a transfer of stress to the eastern Marmara seismic gap.

Paper on earthquake clustering in hydrothermal reservoirs

We published another paper on induced seismicity, this time related to the clustering properties of induced seismicity observed in a couple of hydrothermal reservoirs. Here is the reference:

Martínez-Garzón, P., I. Zaliapin, Y. Ben-Zion, G. Kwiatek, and M. Bohnhoff (2018). Comparative Study of Earthquake Clustering in Relation to Hydraulic Activities at Geothermal Fields in California. Journal of Geophysical Research: Solid Earth, 123. DOI: 10.1029/2017JB014972 [ Article Page ]

New paper on triggering processes in rock fracture experiments

We published a new manuscript in Physical Review Letters on triggering processes in laboratory experiments on rock samples (with implications to natural and induced seismicity of course!)

Reference

Davidsen, J., Kwiatek, G., Charalampidou, E.-M., Goebel, T., Stanchits, S., Rueck, M., and G. Dresen. Triggering processes in rock fracture. Phys. Res. Lett. 119, 068501, DOI: 10.1103/PhysRevLett.119.068501. [ Article Page ]

Abstract: We study triggering processes in triaxial compression experiments under a constant displacement rate on sandstone and granite samples using spatially located acoustic emission events and their focal mechanisms. We present strong evidence that event-event triggering plays an important role in the presence of large-scale or macrocopic imperfections, while such triggering is basically absent if no significant imperfections are present. In the former case, we recover all established empirical relations of aftershock seismicity including the Gutenberg-Richter relation, a modified version of the Omori-Utsu relation and the productivity relation—despite the fact that the activity is dominated by compaction-type events and triggering cascades have a swarmlike topology. For the Gutenberg-Richter relations, we find that the b value is smaller for triggered events compared to background events. Moreover, we show that triggered acoustic emission events have a focal mechanism much more similar to their associated trigger than expected by chance.