scholarly journals Earthquake static stress transfer in the 2013 Valencia Gulf (Spain) seismic sequence

2016 ◽  
Author(s):  
Lluis Salo ◽  
Tanit Frontera ◽  
Xavier Goula ◽  
Lluis Pujades ◽  
Alberto Ledesma
Keyword(s):  
Stress Transfer ◽  
Mediterranean Coast ◽  
Static Stress ◽  
Earthquake Triggering ◽  
Underground Gas Storage ◽  
Focal Mechanism Solutions ◽  
Coulomb Failure ◽  
Final Stress ◽  
Static Stress Change

Abstract. On September 24th, 2013, a ML 3.6 earthquake struck in Valencia Gulf (Spain), near the Mediterranean coast of Castellon, roughly a week after the gas injections conducted in the area to develop an Underground Gas Storage had been halted. The event, felt by the nearby population, led to a sequence build-up of felt events which reached a maximum of ML 4.3 on October 2nd. Here, we study the role of static stress change as an earthquake triggering mechanism during the sequence, and provide quantitative assessment of the known faults final stress state. By means of the Coulomb Failure Function, the evolution of static stress is quantified both on fault planes derived from focal mechanism solutions (which act as source and receiver faults), and on the previously mapped structures in the area (receiver faults). Results show that static stress transfer could have acted as a partial trigger, and point towards an ESE-dipping structure as the most likely to have been activated during the sequence. Based on this approach, the influence of the studied events in the occurrence of future and potentially damaging earthquakes in the area would be, at most, of second order.

scholarly journals Earthquake static stress transfer in the 2013 Gulf of Valencia (Spain) seismic sequence

Solid Earth ◽  
2017 ◽  
Vol 8 (5) ◽  
pp. 857-882 ◽  
Author(s):  
Lluís Saló ◽  
Tànit Frontera ◽  
Xavier Goula ◽  
Luis G. Pujades ◽  
Alberto Ledesma
Keyword(s):  
Stress Transfer ◽  
Mediterranean Coast ◽  
Static Stress ◽  
Earthquake Triggering ◽  
Underground Gas Storage ◽  
Focal Mechanism Solutions ◽  
Stress Changes ◽  
Coulomb Failure ◽  
As Stress

Abstract. On 24 September 2013, an Ml 3.6 earthquake struck in the Gulf of Valencia (Spain) near the Mediterranean coast of Castelló, roughly 1 week after gas injections conducted in the area to develop underground gas storage had been halted. The event, felt by the nearby population, led to a sequence build-up of felt events which reached a maximum of Ml 4.3 on 2 October.Here, we study the role of static stress transfer as an earthquake-triggering mechanism during the main phase of the sequence, as expressed by the eight felt events. By means of the Coulomb failure function, cumulative static stress changes are quantified on fault planes derived from focal mechanism solutions (which act as both source and receiver faults) and on the previously mapped structures in the area (acting only as stress receivers in our modeling). Results suggest that static stress transfer played a destabilizing role and point towards an SE-dipping structure underlying the reservoir (or various with analogous geometry) that was most likely activated during the sequence. One of the previously mapped faults could be geometrically compatible, yet our study supports deeper sources. Based on this approach, the influence of the main events in the occurrence of future and potentially damaging earthquakes in the area would not be significant.

A New Technique to Calculate Earthquake Stress Transfer and to Probe the Physics of Aftershocks

2020 ◽  
Vol 110 (2) ◽  
pp. 863-873 ◽  
Author(s):  
Margarita Segou ◽  
Tom Parsons
Keyword(s):  
Stress Reduction ◽  
Regional Scale ◽  
Stress Transfer ◽  
The United States ◽  
Physical Principle ◽  
Static Stress ◽  
Stress Change ◽  
Earthquake Triggering ◽  
Triggered Earthquakes ◽  
Stress Changes

ABSTRACT Coseismic stress changes have been the primary physical principle used to explain aftershocks and triggered earthquakes. However, this method does not adequately forecast earthquake rates and diverse rupture populations when subjected to formal testing. We show that earthquake forecasts can be impaired by assumptions made in physics-based models such as the existence of hypothetical optimal faults and regional scale invariability of the stress field. We compare calculations made under these assumptions along with different realizations of a new conceptual triggering model that features a complete assay of all possible ruptures. In this concept, there always exists a set of theoretical planes that has positive failure stress conditions under a combination of background and coseismic static stress change. In the Earth, all of these theoretical planes may not exist, and if they do, they may not be ready to fail. Thus, the actual aftershock plane may not correspond to the plane with the maximum stress change value. This is consistent with observations that mainshocks commonly activate faults with exotic orientations and rakes. Our testing ground is the M 7.2, 2010 El Mayor–Cucapah earthquake sequence that activated multiple diverse fault populations across the United States–Mexico border in California and Baja California. We carry out a retrospective test involving 748 M≥3.0 triggered earthquakes that occurred during a 3 yr period after the mainshock. We find that a probabilistic expression of possible aftershock planes constrained by premainshock rupture patterns is strongly favored (89% of aftershocks consistent with static stress triggering) versus an optimal fault implementation (35% consistent). Results show that coseismic stress change magnitudes do not necessarily control earthquake triggering, instead we find that the summed background stress and coseismic stress change promotes diverse ruptures. Our model can thus explain earthquake triggering in regions where optimal plane mapping shows coseismic stress reduction.

scholarly journals Effect of heterogeneities on evaluating earthquake triggering of volcanic eruptions

2013 ◽  
Vol 13 (2) ◽  
pp. 231-237 ◽  
Author(s):  
J. Takekawa ◽  
H. Mikada ◽  
T. Goto
Keyword(s):  
Correlation Length ◽  
Stress Transfer ◽  
Volcanic Eruptions ◽  
Static Stress ◽  
Chamber Wall ◽  
Maximum Effect ◽  
Earthquake Triggering ◽  
Velocity Perturbation ◽  
Failure Pressure ◽  
Scale Heterogeneity

Abstract. Recent researches have indicated coupling between volcanic eruptions and earthquakes. Some of them calculated static stress transfer in subsurface induced by the occurrences of earthquakes. Most of their analyses ignored the spatial heterogeneity in subsurface, or only took into account the rigidity layering in the crust. On the other hand, a smaller scale heterogeneity of around hundreds of meters has been suggested by geophysical investigations. It is difficult to reflect that kind of heterogeneity in analysis models because accurate distributions of fluctuation are not well understood in many cases. Thus, the effect of the ignorance of the smaller scale heterogeneity on evaluating the earthquake triggering of volcanic eruptions is also not well understood. In the present study, we investigate the influence of the assumption of homogeneity on evaluating earthquake triggering of volcanic eruptions using finite element simulations. The crust is treated as a stochastic media with different heterogeneous parameters (correlation length and magnitude of velocity perturbation) in our simulations. We adopt exponential and von Karman functions as spatial auto-correlation functions (ACF). In all our simulation results, the ignorance of the smaller scale heterogeneity leads to underestimation of the failure pressure around a chamber wall, which relates to dyke initiation. The magnitude of the velocity perturbation has a larger effect on the tensile failure at the chamber wall than the difference of the ACF and the correlation length. The maximum effect on the failure pressure in all our simulations is about twice larger than that in the homogeneous case. This indicates that the estimation of the earthquake triggering due to static stress transfer should take account of the heterogeneity of around hundreds of meters.

The formation of the Egyptian Arabic dialect area

2018 ◽  
Author(s):  
Peter Behnstedt ◽  
Manfred Woidich
Keyword(s):  
Mediterranean Coast ◽  
External Factors ◽  
Internal Factors ◽  
Dialect Contact ◽  
Historical Information ◽  
Egyptian Arabic ◽  
Transitional Area ◽  
The Mediterranean

This chapter deals with the sedentary dialects of Egypt, excluding the bedouin dialects of Sinai and the Libyan bedouin dialects on the Mediterranean coast. It attempts to combine historical information on the settlement of Arabic tribes in Egypt with accounts of present-day Egyptian dialects and those of the regions from which those tribes came, initially Yemen and the Levant, later Hejaz, and then the Maghreb. The diversity of the Egyptian Arabic dialect area is partly explained by external factors, namely different layers of arabization over centuries. It is also explained by internal factors, namely dialect contact, which implies phenomena such as hyperdialectisms. Egypt is seen as a dialect area in its own right, but one that shows phenomena of a transitional area between the Arab East and West. A case study of Alexandria deals with dialect death. The role of substrata is discussed, but is considered negligible.

scholarly journals Stress relaxation arrested the mainshock rupture of the 2016 Central Tottori earthquake

2021 ◽  
Vol 2 (1) ◽  
Author(s):  
Yoshihisa Iio ◽  
Satoshi Matsumoto ◽  
Yusuke Yamashita ◽  
Shin’ichi Sakai ◽  
Kazuhide Tomisaka ◽  
...  
Keyword(s):  
Stress Relaxation ◽  
Focal Mechanism ◽  
Large Earthquake ◽  
Static Stress ◽  
Focal Mechanism Solutions ◽  
Large Earthquakes

AbstractAfter a large earthquake, many small earthquakes, called aftershocks, ensue. Additional large earthquakes typically do not occur, despite the fact that the large static stress near the edges of the fault is expected to trigger further large earthquakes at these locations. Here we analyse ~10,000 highly accurate focal mechanism solutions of aftershocks of the 2016 Mw 6.2 Central Tottori earthquake in Japan. We determine the location of the horizontal edges of the mainshock fault relative to the aftershock hypocentres, with an accuracy of approximately 200 m. We find that aftershocks rarely occur near the horizontal edges and extensions of the fault. We propose that the mainshock rupture was arrested within areas characterised by substantial stress relaxation prior to the main earthquake. This stress relaxation along fault edges could explain why mainshocks are rarely followed by further large earthquakes.

Sign in / Sign up

Export Citation Format

Share Document