scholarly journals Influences of recurrence times and fault zone temperatures on the age-rate dependence of subduction zone seismicity

1997 ◽  
Vol 102 (B10) ◽  
pp. 22839-22854 ◽  
Author(s):  
Robert McCaffrey
Baltica ◽  
2021 ◽  
pp. 157-173
Author(s):  
Serkan Öztürk

The main objective of this work is to make detailed region-time-magnitude analyses by describing the statistical behaviours of earthquakes in the Central Anatolian Region of Turkey. In this scope, several seismic and tectonic parameters such as Mcomp, b-value, Dc-value, Z-value, recurrence times and annual probabilities were evaluated. For the analyses, a homogeneous catalogue including 10,146 earthquakes with 1.0 ≤ Md ≤ 5.7 between 30 July 1975 and 29 December 2018 was used and spatio-temporal changes of earthquake behaviours were mapped for the beginning of 2019. Earthquake magnitudes varied from 1.9 to 3.0 on average, and hence Mcomp was considered to be 2.6. The b-value was calculated as 1.26 ± 0.07, and this relatively large value indicates that small-magnitude events are dominant. The Dc-value was computed as 1.31 ± 0.03. This small value means that distances between epicentres approach the diameter of the cluster, and seismic activity is more clustered at smaller scales or in larger regions. The spatio-temporal analyses of recurrence times suggest that the Central Anatolian Region has an intermediate/long-term earthquake hazard in comparison to occurrences of strong earthquakes in the short term. Several anomaly regions of a small b-value and a large Z-value were found in and around the Tuzgölü Fault Zone, Central Anatolian Fault Zone, Salanda fault and Niğde fault at the beginning of 2019. Thus, a combination of the regions with a lower b-value, a higher Z-value and also moderate recurrence times may give significant clues for the future possible earthquakes, and detected regions may be thought to be the most likely areas for strong/large events in the Central Anatolian Region.


1977 ◽  
Vol 67 (1) ◽  
pp. 233-241
Author(s):  
Bruce M. Douglas ◽  
Alan Ryall

abstract A method is described for determining recurrence times as a function of distance to the causative fault and magnitude, for earthquakes distributed along a linear source zone. The method takes into account rupture length, which is scaled to magnitude, and permits direct calculation of approximate return periods for peak ground-motion parameters for large earthquakes, when the appropriate attenuation functions are known. Several examples are presented using instrumentally determined seismicity along the San Andreas fault zone. Results illustrate the necessity of incorporating rupture length in calculations related to seismic risk; for large earthquakes, it is also necessary to use a source region large enough to contain the rupture zones of all such events. For a site in the San Andreas fault zone we find that the recurrence time to be within 10 km of the causative fault of an earthquake with M ≧ 8 is 200 to 300 years, depending on the choice of maximum magnitude (8.6 or 8.4). For a site on the fault in the Hollister region, we find that recurrence times to be within 10 km of the rupture due to events of M ≧ 5, 6 and 7 are, respectively, 12, 45 and 105 years.


2020 ◽  
Author(s):  
Nicolai Nijholt ◽  
Wim Simons ◽  
Riccardo Riva

<p>Two major fault systems host M<sub>w</sub>>7 earthquakes in Central and Northern Sulawesi, Indonesia: the Minahassa subduction interface and the Palu-Koro strike-slip fault. The Celebes Sea oceanic lithosphere subducts beneath the north arm of Sulawesi at the Minahassa subduction zone. At the western termination of the Minahassa subduction zone, it connects to the left-lateral Palu-Koro strike-slip fault zone. This fault strikes onshore at Palu Bay and then crosses Sulawesi. Interseismic GNSS velocities indicate that the Palu-Koro fault zone accommodates about 4 cm/yr of relative motion in the Palu Bay area, with a ~10 km locking depth. This shallowly locked segment of the Palu-Koro fault around the Palu Bay area ruptured during the devastating, tsunami-generating, 2018 M<sub>w</sub>7.5 Palu earthquake. This complex event highlights the high seismic hazard for the island of Sulawesi.</p><p>We have a >20-year record of GNSS velocities on Sulawesi, where the densest cluster of monument sites surrounds the Palu-Koro fault, specifically around Palu Bay, whereas the rest of the island is less densely covered. High quality estimates of interseismic velocities reveal second-order complex patterns of transient deformation in the wake of major earthquakes: the velocities in northern Sulawesi and around the Palu-Koro fault do not follow their interseismic trends after a major subduction earthquake has occurred, for several years after the event. This effect of transient deformation reaches more than 400km away from the epicentre of the major earthquakes. Surprisingly, a deviation from the background slip rate on the Palu-Koro fault is not accompanied by a deviation from the background (micro)seismic activity.</p><p>We construct a 3D numerical model based on the structural and seismological data in the Sulawesi region. We investigate the post-seismic relaxation pattern from a subduction earthquake and determine whether the slip rate on the Palu-Koro fault changes due to this earthquake through forward model calculations. With a modelling focus on the 1996 M<sub>w</sub>7.9 and 2008 M<sub>w</sub>7.4 earthquakes that ruptured the Minahassa subduction interface, this study outlines the triggering of transient deformation and continual interaction between the Minahassa subduction interface and the Palu-Koro strike-slip fault.</p>


2004 ◽  
Vol 109 (B10) ◽  
Author(s):  
Martine Simoes ◽  
Jean Philippe Avouac ◽  
Rodolphe Cattin ◽  
Pierre Henry

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