Seismic source study of the 1989, October 29, Chenoua (Algeria) earthquake from aftershocks, broad-band and strong ground motion records

The broad-band teleseismics records of the earthquake of October 29,1989 in Algeria (MW = 6.0) allow a detailed study of the rupture process of this earthquake. The focal mechanism obtained by P and SH modeling corresponds to reverse faulting with a small amount of left-lateral movement along a fault striking 246° and dipping 56°. The rupture is found to be complex with two sub-events separated in time but occurring on the same plane. The lowfrequency records of an accelerometer located some 25 km to the west of the main shock are also better fi tted when the rupture is composed of a double pulse. In the two cases, there is strong evidence for the rupture to propagate from south-west towards north-east.The relocalisation of the main shock by using a master-event technique and the data from Italian and Spanish stations led to the same conclusions. Soon after the main event, a temporary seimic network was installed in the epicentral area. The aftershock clouds defi ne a SW-NE fault dipping to the NW compatible with the results of the modelisations of the teleseismic body-waves and the accelerogram. The focal mechanisms correspond mainly to reverse faulting. The maximum principal direction of the stress tensor obtained from the inversion is about N-S and the minimum is vertical, typical of a compressive regime. The Chenoua earthquake took place on a fault which was not recognized as active. Repeated comparable seismic events on this fault and on the fault that borders the massif to the south explain this intriguing topographic feature

A FIRST-AND SECOND-ORDER TURBULENCE MODELS IN HYDROGEN NON-PREMIXED FLAME

ABSTRACT The mathematical modelling of turbulent flames is a difficult task due to the intense coupling between turbulent transport processes and chemical kinetics. The model presented within this paper is focused on the turbulence-chemistry interaction. The topic of this study is the numerical simulation of turbulent non-premixed hydrogen flame with different turbulent models in order to invest gate their predictive capability. The two turbulent models are compared: the (k-ε) model with a limited Pope's correction and the Reynolds stress model (RSM). The predictions are validated against experimental data provided by Raman and laser Doppler anemometry (LDA) measurements for a turbulent jet hydrogen-air diffusion flame. The turbulence-chemistry interaction is handled with flame let approach. Simulations of test cases with simple geometries verify the developed model and compare favourably with results of earlier investigations that employed both (k-ε) and RSM closures with the CMC and PDF approache

Heat Transfer in Turbulent Boundary Layers of Conical and Bell Shaped Rocket Nozzles with Complex Wall Temperature

WOS:000335865300005International audienceThe objective of this article is to perform detailed analysis of heat transfer in accelerated supersonic nozzle flows with cooled walls. Since most of the heat transfer occurs near the nozzle walls, correct prediction of the boundary layer under strong adverse pressure gradient is therefore required to achieve high fidelity numerical prediction. In this study, a two-equation SST-V turbulence model is used in conjunction with a second-order explicit-implicit method to solve axisymmetric compressible Navier-Stokes equations. First, the effect of the inlet pipe diameter and the associated contraction area on the heat transfer is studied in nozzles having 15 degrees and 30 degrees diverging half-angles. Then, a series of computations are conducted to examine the efficiency of the use of a constant wall temperature as a function of the stagnation temperature in heat transfer calculations. The computations are performed for nominal stagnation pressure of 208N/cm(2) and stagnation temperature of 539K. The computed heat-transfer coefficients are compared to experimental data and a good agreement is found. A pronounced increase in the throat heat transfer coefficient peak is observed accompanied with a reduction in the contraction area ratio. Also, the peak of the heat transfer coefficient for the pipe inlet diameter of 7.8cm is found to be 70% higher than the one related to the pipe of 16.51cm diameter

Three dimensional velocity structure and relocated aftershocks for the 1985 Constantine, Algeria (MS = 5.9) earthquake

Local earthquake travel-time data were inverted to obtain a three dimensional tomographic image of the region centered on the 1985 Constantine earthquake. The resulting velocity model was then used to relocate the events. The tomographic data set consisted of P and S waves travel-times from 653 carefully selected aftershocks of this moderate size earthquake, recorded at 10 temporary stations. A three-dimensional P-wave velocity image to a depth of 12 km was obtained by Thurber's method. At shallower depth, the velocity contrasts reflected the differences in tectonic units. Velocities lower than 4 km/s corresponded to recent deposits, velocities higher than 5 km/s to the Constantine Neritic and the Tellian nappes. The relocation of the aftershocks indicates that most of the seismicity occured where the velocity exceeded 5.5 km/s. The aftershock distribution accurately defined the three segments involved in the main shock and led to a better understanding of the rupture process

Three dimensional velocity structure and relocated aftershocks for the 1985 Constantine, Algeria (MS = 5.9) earthquake

Local earthquake travel-time data were inverted to obtain a three dimensional tomographic image of the region centered on the 1985 Constantine earthquake. The resulting velocity model was then used to relocate the events. The tomographic data set consisted of P and S waves travel-times from 653 carefully selected aftershocks of this moderate size earthquake, recorded at 10 temporary stations. A three-dimensional P-wave velocity image to a depth of 12 km was obtained by Thurber's method. At shallower depth, the velocity contrasts reflected the differences in tectonic units. Velocities lower than 4 km/s corresponded to recent deposits, velocities higher than 5 km/s to the Constantine Neritic and the Tellian nappes. The relocation of the aftershocks indicates that most of the seismicity occured where the velocity exceeded 5.5 km/s. The aftershock distribution accurately defined the three segments involved in the main shock and led to a better understanding of the rupture process

The Constantine (Algeria) seismic sequence of 27 October 1985: a new rupture model from aftershock relocation, focal mechanisms, and stress tensors

International audienceThe October 27, 1985 Constantine earthquake of magnitude MS 5.9 (NEIC) although moderate is the strongest earthquake recorded in the eastern Tellian Atlas (northeast Algeria) since the beginning of instrumental seismology. The main shock locations given by different institutions are scattered and up to 10 km away northwest from the NE-SW 30 km long elongated aftershocks cloud localized by a dedicated temporary portable network. The focal mechanism indicates left-lateral strike-slip on an almost vertical fault with a small reverse component on the northwest dipping plane. This paper presents relocations of the main shock and aftershocks using TomoDD. One hundred thirty-eight individual focal mechanisms have been built allowing the determination of the stres