Energy partitioning during seismic slip in pseudotachylyte-bearing faults (Gole Larghe Fault, Adamello, Italy)   总被引：1，自引：0，他引：1  

Lidia Pittarello  Giulio Di Toro  Andrea Bizzarri  Giorgio Pennacchioni  Jafar Hadizadeh  Massimo Cocco 《Earth and Planetary Science Letters》2008,269(1-2):131-139

The determination of the earthquake energy budget remains a challenging issue for Earth scientists, as understanding the partitioning of energy is a key towards the understanding the physics of earthquakes. Here we estimate the partition of the mechanical work density into heat and surface energy (energy required to create new fracture surface) during seismic slip on a location along a fault. Earthquake energy partitioning is determined from field and microstructural analyses of a fault segment decorated by pseudotachylyte (solidified friction-induced melt produced during seismic slip) exhumed from a depth of ~ 10 km—typical for earthquake hypocenters in the continental crust. Frictional heat per unit fault area estimated from the thickness of pseudotachylytes is ~ 27 MJ m^− 2. Surface energy, estimated from microcrack density inside clast (i.e., cracked grains) entrapped in the pseudotachylyte and in the fault wall rock, ranges between 0.10 and 0.85 MJ m^− 2. Our estimates for the studied fault segment suggest that ~ 97–99% of the energy was dissipated as heat during seismic slip. We conclude that at 10 km depth, less than 3% of the total mechanical work density is adsorbed as surface energy on the fault plane during earthquake rupture.  相似文献   

Polar wander of Mars: Evidence from giant impact basins     

Jafar Arkani-Hamed 《Icarus》2009,204(2):489-498

We investigate the polar wander of Mars in the last ∼4.2 Ga. We identify two sets of basins from the 20 giant impact basins reported by Frey [Frey, H., 2008. Geophys. Res. Lett. 35, L13203] which trace great circles on Mars, and propose that the great circles were the prevailing equators of Mars at the impact times. Monte Carlo tests are conducted to demonstrate that the two sets of basins are most likely not created by random impacts. Also, fitting 63,771 planes to randomly selected sets of 5, 6, or 7 basins indicated that the identified two sets are unique. We propose three different positions for the rotation pole of Mars, besides the present one. Accordingly, Tharsis bulge was initially formed at ∼50 N and moved toward the equator while rotating counterclockwise due to the influence of the two newly forming volcanic constructs, Alba Patera and Elysium Rise. The formation of the giant impact basins, subsequent mass concentrations (mascons) in Argyre, Isidis, and Utopia basins, and surface masses of volcanic mountains such as Ascraeus, Pavonis, Arsia and Olympus, caused further polar wander which rotated Tharsis bulge clockwise to arrive at its present location. The extensive polar motion of Mars during 4.2-3.9 Ga implies a weak lithosphere on a global scale, deduced from a total of 72,000 polar wander models driven by Tharsis bulge, Alba Patera and Elysium Rise as the major mass perturbations. Different compensation states, 0-100%, are examined for each of the surface loads, and nine different thicknesses are considered for an elastic lithosphere. The lithosphere must have been very weak, with an elastic thickness of less than 5 km, if the polar wander was driven by these mass perturbations.  相似文献   

Comparative analysis on macroscale material models for the prediction of masonry in-plane behavior     

Zizi  Mattia  Chisari  Corrado  Rouhi  Jafar  De Matteis  Gianfranco 《Bulletin of Earthquake Engineering》2022,20(2):963-996

Bulletin of Earthquake Engineering - Simulating the mechanical behavior of masonry structures with reasonable approximation using numerical models is a complex issue, mainly due to the...  相似文献   

An integrated GIS-based approach for geohazards risk assessment in coal mines     

Vahid Vaziri  Jafar Khademi Hamidi  Ahmad Reza Sayadi 《Environmental Earth Sciences》2018,77(1):29

From the viewpoint of safety in underground coal mining, the most suitable mining panel is the one with minimum geological structures, the right machinery, and equipment selection, trained employee, and proficient stope management. Since the ground parameters are uncontrollable and inherent uncertainties exist, a high percent of risk will usually accompany the underground coal mining activities. The main purpose of this study is to present a geological–geotechnical risk assessment model for identification of high risk-prone areas in underground coal mines using an integrated GIS-geostatistics system. Tabas as the first mechanized and largest underground coal mine in Iran was selected as a case study in this study. Gas content of coal seam, Coal Mine Roof Rating (CMRR), initial in situ stress state, fault throw, and orientation were selected as hazard/risk factors. For estimating the amount of coal seam gas content, CMRR and initial in situ stress in unsampled areas and providing the prediction maps, geostatistics module in ArcGIS was used. Rock engineering system–interaction matrix method was used for attribute weight assignment. Next, the attribute layers were weighted, rated, and overlaid to create a final map of geohazards risk. The analysis results of final risk map indicate that about 45% of under study area is prone to high to very high geohazards risk. Comparison of the results with experiences obtained during the early part of the mine and mined-out panels showed generally good agreement with promising ideas. This highlights the potential application of the GIS-based approach for hazards detection and geohazards risk assessment in underground coal mines.  相似文献   

On the effects of higher convection modes on the thermal evolution of small planetary bodies     

Jafar Arkani-Hamed 《Earth, Moon, and Planets》1979,20(4):397-413

The effects of higher modes of convection on the thermal evolution of a small planetary body is investigated. Three sets of models are designed to specify an initially cold and differentiated, an initially hot and differentiated, and an initially cold and undifferentiated Moon-type body. The strong temperature dependence of viscosity enhances the thickening of lithosphere so that a lithosphere of about 400 km thickness is developed within the first billion years of the evolution of a Moon-type body. The thermally isolating effect of such a lithosphere hampers the heat flux out of the body and increases the temperature of the interior, causing the solid-state convection to occur with high velocity so that even the lower modes of convection can maintain an adiabatic temperature gradient there. It is demonstrated that the effect of solid-state convection on the thermal evolution of the models may be adequately determined by a combination of convection modes up to the third or the fourth order harmonic. The inclusion of higher modes does not affect the results significantly.  相似文献   

On the moments of inertia differences of the moon     

Jafar Arkani-Hamed  Mehdi B. Kermani 《Earth, Moon, and Planets》1977,17(2):167-176

In this paper it is shown that the differences of the moments of inertia of the Moon are, most likely, due to the surface irregularities, the over-all front side mare fillings and the backside topography.  相似文献   

Low-magnetic crust underlying South Province of Mars     

Jafar Arkani-Hamed  Daniel Boutin 《Icarus》2012,217(1):209-230

The lack of distinct magnetic signatures observed by Mars Global Surveyor (MGS) over the impact craters and impact-related Quasi-Circular-Depressions (QCDs) with diameters greater than 200 km located on South Province, south of 30S and from almost the west of Hellas to Argyre basins, implies a weakly magnetized crust. Using MOLA topography and the recent JPL gravity model of Mars we determine the structure of the crust beneath the craters and impact-related QCDs, and show that the impacts that have created these features were capable of strongly disturbing the crust directly beneath. On the basis of theoretical magnetic anomaly modeling and shock demagnetization models, we demonstrate that the impacts are capable of demagnetizing the entire crust beneath and creating distinct magnetic anomalies at the satellite altitude of 400 km in case the crust was appreciably magnetized prior to the impacts. We derive the magnetic anomalies of these features using the radial component of the high-altitude nighttime MGS data. An upper limit of <2 × 10⁴ A for the bulk magnetization of the crust beneath South Province is estimated, which is about 30 times less than that underlying Terra Cimmeria and Terra Sirenum. Similar weak bulk magnetization is obtained for part of the crust surrounding Hellas, Isidis, and Argyre basins.  相似文献   

Hazards of mechanized tunnel excavation in H<Subscript>2</Subscript>S bearing ground in Aspar tunnel,Iran     

Hossein Mirmehrabi  Mohammad Ghafoori  Gholamreza Lashkaripour  Sadegh Tarigh Azali  Jafar Hassanpour 《Environmental Earth Sciences》2012,66(2):529-535

Occurrence of hydrogen sulfide gas (H₂S) is one of the most important engineering geological hazards during tunneling. Its hazards and consequent challenges are very difficult and costly to solve. During site investigation, one of the tasks for engineering geologists is prediction and evaluation of the risk of H₂S gas in the underground spaces. In this study, water conveyance tunnel of Aspar, which was excavated in H₂S-bearing environments, is discussed. The tunnel is excavated in the hydrocarbon formations. Applied experiments suggest that geological formations pertaining to hydrocarbon resources are crucial in formation and reservation of H₂S gas. This paper briefly discusses hazards and geological sources of H₂S, as well as remedial measures for decreasing the risks and problems in excavation of the tunnel. To predict the risk of H₂S gas in the underground spaces, it is possible to use some precursors such as: sulfur springs, organic traces, organic argillaceous rocks, exposure of H₂S odor from fresh surface of rock and smell of H₂S during boreholes drilling. Controlling the inflow of groundwater into the excavation, diluting the concentration of H₂S, training the personnel and utilization of some proper safety equipment have been used to mitigate risks and problems in tunnel excavation.  相似文献   

Integrating GIS and DSS for identification of suitable areas for artificial recharge,case study Meimeh Basin,Isfahan, Iran   总被引：12，自引：0，他引：12  

Jafar?GhayoumianEmail author  B.?Ghermezcheshme  S.?Feiznia  A.?A.?Noroozi 《Environmental Geology》2005,47(4):493-500

Flood spreading is an inexpensive method for flood mitigation and artificial recharge of aquifers that results in a large budget return for relatively small investment.It is necessary to study some regional characteristics in order to determine the appropriate areas for artificial groundwater recharge by flood spreading in Meimeh Basin, Isfahan Province, Iran. Necessary regional characteristics to be studied are: slope, infiltration rate, sediment thickness, transmissivity, and water quality. In this research to identify suitable areas for artificial recharge several thematic layers were prepared, assigning each layer to one of the mentioned characteristics. The thematic layers were classified to several classes based on the existing criteria. All of the classes of the thematic layers were integrated and analyzed using a decision support system (DSS) in a geographical information system (GIS) environment. Finally suitability of the integrated classes for artificial recharge was identified in which the following classes were separated:(i) Very suitable, (ii) suitable, (iii) moderate suitability, and (iv) unsuitable.The validity of the generated model was verified by applying the model to a number of successful floodwater spreading stations throughout Iran. The verified model showed satisfactory results for all of the stations. The results for Meimeh Basin showed that about 70% of the Quaternary sediments in the studied area are suitable and moderately suitable for artificial recharge by flood spreading.  相似文献   

Lunar mascons as consequences of giant impacts     

Jafar Arkani-Hamed 《Earth, Moon, and Planets》1974,10(3-4):307-322

A model is proposed for the formation of lunar mascons which explains persistence of lunar mascons for more than 3 b.y., evidence for the volcanic activity 3.7-3.2 b.y. ago, and negative gravity anomalies surrounding the mascons. It is concluded that mascons have resulted from the perturbations introduced by the giant impacts into an otherwise spherically symmetric Moon; a giant impact enhances the rate of cooling beneath the impact site by introducing releatively low temperature to a deeper part of the Moon through forming a basin and also by removing substantial amount of radioactive material by means of ejecta. On the other hand, it reduces the rate of cooling beneath the surrounding highland by thermal insulation through extensive fracturing and covering by an ejecta blanketing. Consequently, the base of the lithosphere (100 km thick) beneath the highland remelts to a depth of about 80 km and this creates thermal stresses strong enough to open the fractures in the overlying region and to cause magmatization and volcanic activity. Persistence of the molten phase around 100 km depth for about 1 b.y. probably provides further differentiation and an upward concentration of low density material, giving rise to the observed negative gravity rings. On the other hand, the relatively cold lithosphere beneath the basin forms a layer strong enough to support the associated mascon.  相似文献