Regularity patterns and zones of seismic potential for future large earthquakes in the mediterranean region

Purcaru, G.; Berckhemer, H.

doi:10.1016/0040-1951(82)90073-7

Cited by 26 publications

(3 citation statements)

References 27 publications

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“…During the last century, several strong earthquakes have taken place along the NAF. These events or subsets of them have been the subject of numerous studies (Mogi, 1968;Toksöz et al, 1979;Purcaru and Berckhemer, 1982;Roth, 1988;Stein et al, 1997). There are several reasons for the interest: first, the events provide an unequalled possibility to analyse how the occurrence of an earthquake may trigger additional shocks.…”

Section: Introductionmentioning

confidence: 99%

Elastic and inelastic triggering of earthquakes in the North Anatolian Fault zone

2006

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Deformation models used for explaining the triggering mechanism often assume pure elastic behaviour for the crust and upper mantle. In reality however, the mantle and possibly the lower crust behave viscoelastically, particularly at long-term scale. Consequently, the stress field of an earthquake is in general time dependent. In addition, if the elastic stress increase were enough to trigger a later earthquake, this triggered event should occur instantaneously and not many years later. Hence, it is adequate to include inelastic behaviour when analysing stress transfer and earthquake interaction.In this work, we analyse a sequence of 10 magnitude M s > 6.5 events along the North Anatolian Fault between 1939 and 1999 to study the evolution of the Coulomb stress field.We investigate the triggering of events in the series by stress transfer, taking viscoelastic relaxation into account. We evaluate the contribution of elastic stress changes, of post-seismic viscoelastic relaxation in the lower crust and mantle, and of steady tectonic loading to the total Coulomb stress field. We analyse the evolution of stress in the region under study, as well as on the rupture surfaces of the considered events and their epicentres. We study the state of the Coulomb stress field before the 1999 Izmit and Düzce earthquakes, as well as in the Marmara Sea region.In general, the Coulomb stress failure criterion offers a plausible explanation for the timing and location of the events in this area and for this sequence of events. However, we show that using a purely elastic model disregards an important part of the actual stress increase/decrease. In several cases, post-seismic relaxation effects are important and greater in magnitude than the stress changes due to steady tectonic loading. Consequently, viscoelastic relaxation should be considered in any study dealing with Coulomb stress changes. of 39According to our study, and assuming that an important part of the rupture surface must be stressed for an earthquake to occur, the most likely value for the viscosity of the lower crust or mantle in this region is 5⋅10 17 -10 18 Pa⋅s. Our results also suggest that other time-dependent processes apart from viscoelastic relaxation might have been involved in the triggering of the 1999 Düzce event. Finally, we argue that the Marmara Sea region is currently being loaded with positive Coulomb stresses at a much faster rate than would arise exclusively due to steady tectonic loading on the North Anatolian Fault.

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Section: Introductionmentioning

confidence: 99%

Elastic and inelastic triggering of earthquakes in the North Anatolian Fault zone

2006

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“…This same compressional trend has been mapped on land, where it is dated primarily as lower Quaternary (Rouvier, 1977). This compression, recording the continued motion of Africa northward (Auzende et al, 1972;Purcaru and Berckhemer, 1982), is superposed on the major Miocene deformation cited above. Displacement of the type leading to compression of structures in northern Tunisia and the adjacent margin is probably comparable to that presently affecting Algeria; evidence for the latter includes powerful earthquakes, such as the 1954 Orleansville and the 1980 El Asnam events (Lepvrier, 1981;King, 1981).…”

Section: Structural Trendsmentioning

confidence: 84%

Neogene to Recent Displacement and Contact of Sardinian and Tunisian Margins, Central Mediterranean

Gennesseaux¹

1983

Smithsonian Contributions to the Marine Sciences

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Gennesseaux, Maurice G., and Daniel Jean Stanley. Neogene to Recent Displacement and Contact of Sardinian and Tunisian Margins, Central Mediterranean. Smithsonian Contributions to the Marine Sciences, number 23, 21 pages, 9 figures, 1983.-The seafloor between Sardinia, Tunisia, and Sicily occupies a key sector essential for understanding the geological evolution of the central Mediterranean. Although plate motion is generally considered as an explanation, this structurally complex region remains poorly defined. To interpret better the Neogene evolution, we prepared a detailed bathymetric chart and a map showing structural provinces and post-Miocene sediment patterns, which are constructed on the basis of seismic data (primarily a dense network of 30 KJ Sparker and 3.5 kHz profiles). The data suggest that the present-day configuration of the Tunisian and Sardinian margins results, in large part, from the contact of the southern part of the Corsican-Sardinian microplate with North Africa. Several dominant structural-stratigraphic trends are recognized in this study area: (1) NNW-SSE and NW-SE trends in the northwestern part of the study area are most likely related to the formation of the Algero-Balearic Basin since the late Oligocene. (2) Pronounced NNE-SSE trending structural axes (largely normal faults) are related to the near-parallel (N-S) tilted fault blocks in the Tyrrhenian Sea east of Sardinia. One of these tectonic structures on the margin east of Sardinia may possibly extend southward (190°-200°) onto, and across, the Tunisian margin. The largest, most obvious physiographic features south of Sardinia, including seamounts, ridges, and canyons, are associated with these trends. These features, for the most part of middle to upper Miocene age, are believed closely related to the opening and subsidence of the Tyrrhenian Sea. (3) Morphological, structural, and stratigraphic-sedimentary trends, particularly off Tunisia, suggest Pliocene-Quaternary compression (E-W trending tectonics and depositional axes), resulting from the northward movement of Africa. (4) Important NW-SE structural-depositional trends (many extensional, some strike-slip) of Miocene to Quaternary age dominate the Strait of Sicily area east of Tunisia and south of Sicily. These may be related to displacement along the Calabrian-Sicilian Arc and to a collisional regime between the arc, the Corsican-Sardinian block, and African margin. We believe that the present configuration of the two margins resulted from plate contact and welding during several major Miocene events and also from subsidence, first, of the Algero-Balearic Basin and, then, of the Tyrrhenian Sea. In theory, the Tunisian margin and adjacent land have been subjected to compression as a result of seafloor spreading and collision. The physiographic trends and subsurface structural-stratigraphic configuration we map, however, reveal a predominance of Neogene to Recent structures, primarily of extensional origin. OFFICIAL PUBLICATION DATE is handstamped in a limited number of initia...

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“…In certain regions of the earth, even with a quite different tectonic framing, the seismic pattern is similar: a medium to high seismic risk with a long period of low seismicity interrupted by major earthquakes (M > 7.5). With particularities, this is the case of the Mediterranean region from Iran to the Azores archipelago (Purcaru and Berckhemer 1982), the Greater San Francisco Bay region (Bufe and Varnes 1993) or the Himalayan mountain system (Avouac 2003).…”

Section: Seismic Risk and The Main Aims Of The Studymentioning

confidence: 99%

Perceptions of pre-service teachers on seismic risk and their implications for science education: a comparative study between Spain and Portugal

Almeida

Fernández

Rodrigues

2019

Journal of Risk Research

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This study investigated the importance given by two groups of pre-service teachers of primary education from Spain and Portugal to seismic risk in a framework of different natural risks, both in personal terms and as future teachers. A questionnaire was used for data collection. Some questions about the seismic phenomenon were also included. The sample groups consisted of 110 students from an institution in Spain and 121 from one in Portugal. Both institutions are in cities affected by the historic Lisbon earthquake of 1755. The results showed that the risk of forest fire was the first choice for classroom study in both cases. The Spanish group was also more focused on the importance of other risks like flood and drought. The Portuguese group showed a greater concern with seismic risk, frequently referring to their own historic earthquake of 1755. A few gaps in knowledge concerning earthquake prediction and comparing seismic risk in different regions of their own countries were also found. In accordance with the results, it is suggested that training courses for primary school teachers should include Disaster Risk Education in Science Education for a better understanding of the impact of various hazards and a greater concern with seismic risk due to its particular features, especially in regions where the seismic pattern is characterized by long seismic cycles with major earthquake episodes.

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Regularity patterns and zones of seismic potential for future large earthquakes in the mediterranean region

Cited by 26 publications

References 27 publications

Elastic and inelastic triggering of earthquakes in the North Anatolian Fault zone

Elastic and inelastic triggering of earthquakes in the North Anatolian Fault zone

Neogene to Recent Displacement and Contact of Sardinian and Tunisian Margins, Central Mediterranean

Perceptions of pre-service teachers on seismic risk and their implications for science education: a comparative study between Spain and Portugal

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