Reply to ‘Comment on “The beginnings of hydrous mantle wedge melting” by Till et al.’ by Green, Rosenthal and Kovacs

The comment of Green et al. debates the interpretation of the temperature of the H₂O-saturated peridotite solidus and presence of silicate melt in the experiments of Till et al. (Contrib Mineral Petrol 163:669–688, 2012) at <1,000?°C. The criticisms presented in their comment do not invalidate any of the most compelling observations of Till et al. (Contrib Mineral Petrol 163:669–688, 2012) as discussed in the following response, including the changing minor element and Mg# composition of the solid phases with increasing temperature in our experiments with 14.5?wt% H₂O at 3.2?GPa, as well as the results of our chlorite peridotite melting experiments with 0.7?wt% H₂O. The point remains that Till et al. (Contrib Mineral Petrol 163:669–688, 2012) present data that call into question the H₂O-saturated peridotite solidus temperature preferred by Green (Tectonophysics 13(1–4):47–71, 1972; Earth Planet Sci Lett 19(1):37–53, 1973; Can Miner 14:255–268, 1976); Millhollen et al. (J Geol 82(5):575–587, 1974); Mengel and Green (Stability of amphibole and phlogopite in metasomatized peridotite under water-saturated and water-undersaturated conditions, Geological Society of Australia Special Publication, Blackwell, pp 571-581, 1989); Wallace and Green (Mineral Petrol 44:1–19, 1991) and Green et al. (Nature 467(7314):448–451, 2010).     

Applicability of different ground-motion prediction models for northern Iran

A total of 163 free-field acceleration time histories recorded at epicentral distances of up to 200 km from 32 earthquakes with moment magnitudes ranging from M _w 4.9 to 7.4 have been used to investigate the predictive capabilities of the local, regional, and next generation attenuation (NGA) ground-motion prediction equations and determine their applicability for northern Iran. Two different statistical approaches, namely the likelihood method (LH) of Scherbaum et al. (Bull Seismol Soc Am 94:341–348, 2004) and the average log-likelihood method (LLH) of Scherbaum et al. (Bull Seismol Soc Am 99:3234–3247, 2009), have been applied for evaluation of these models. The best-fitting models (considering both the LH and LLH results) over the entire frequency range of interest are those of Ghasemi et al. (Seismol 13:499–515, 2009a) and Soghrat et al. (Geophys J Int 188:645–679, 2012) among the local models, Abrahamson and Silva (Earthq Spectra 24:67–97, 2008) and Chiou and Youngs (Earthq Spectra 24:173–215, 2008) among the NGA models, and finally Akkar and Bommer (Seism Res Lett 81:195–206, 2010) among the regional models.     

Paleogeographical restoration and ramp tectonic evidence in Tunisian Tellian domain: Ain El Bey-Bou Awen area

The imbrication’s area in northern Tunisia is the most external segment of Alpine range, where several associated folds types with thrust ramps are recognized within imbricate units beneath Numidian front slope. Their presence help to understand thrusting mechanisms installation through studied area. In fact, this zone was considered as a result of Paleogene gravitary slop (Kujawski (Ann Miner Géol Tunis (24):281, 1969); Caire (Ann Min Géol Tunis 26:87–110, 1973); Rouvier 1977), which is proved to be affected by major deep decollement, given rise to various structures, some are propagation folds, specific of foreland front, limited to this area, and those in more external position: Tunisian Atlas (Creusot et al. (C R Acad Sci Paris 314(Sér II):961–965, 1992); Ouali and Mercier (PII: S0191-8141(97):00048-5, 1997); Ouali 1984; Ahmadi et al. (J Struct Geol 28:721–728, 2006)). Various categories of fold ramps could be identified: frontal folds ramp NE–SW and others as lateral or oblique ramp with NW–SE trend (Aridhi et al. (C R Geosci 343:360–369, 2011)). The relation between various structures has been used as recognition tools of thrusting sequences and to propose a new deformation chronology. Delimited outcropping of these structures between two both parallel faults strikes with regional displacement, leads to interpret these faults as cogenetic tear faults of propagation thrusts; this fault separates two domains with different deformation styles from each other side.     

Comment on “A Comparison of Modified Fuzzy Weights of Evidence,Fuzzy Weights of Evidence,and Logistic Regression for Mapping Mineral Prospectivity” by Daojun Zhang,Frits Agterberg,Qiuming Cheng,and Renguang Zuo Math Geosci DOI 10.1007/s11004-013-9496-8

Despite a missing definition of equivalence of mathematical models or methods by Zhang et al. (Math Geosci, 2013), an “equivalence” (Zhang et al., Math Geosci, 2013, p. 6,7,8,14) of modified weights-of-evidence (Agterberg, Nat Resour Res 20:95–101, 2011) and logistic regression does not generally exist. Its alleged proof is based on a previously conjectured linear relationship between weights of evidence and logistic regression parameters (Deng, Nat Resour Res 18:249–258, 2009), which does not generally exist either (Schaeben and van den Boogaart, Nat Resour Res 20:401–406, 2011). In fact, an extremely simple linear relationship exists only if the predictor variables are conditionally independent given the target variable, in which case the contrasts, i.e., the differences of the weights, are equal to the logistic regression parameters. Thus, weights-of-evidence is the special case of logistic regression if the predictor variables are binary and conditionally independent given the target variable.     

Convergence of iterative coupling for coupled flow and geomechanics

In this paper, we study solving iteratively the coupling of flow and mechanics. We demonstrate the stability and convergence of two widely used schemes: the undrained split method and the fixed stress split method. To our knowledge, this is the first time that such results have been rigorously obtained and published in the scientific literature. In addition, we propose a new stress split method, with faster convergence rate than known schemes. These results are specially important today due to the interest in hydraulic fracturing (Dean and Schmidt SPE J. 14:707–714, 2009; Ji et al. SPE J. 14:423–430, 2009; Samier and De Gennaro 2007; Settari and Maurits SPE J. 3:219–226, 1998), in oil and gas shale reservoirs.     

Investigation of the variability of strong ground motions from Vrancea earthquakes

A systematic investigation of the applicability of several ground motion prediction models for Vrancea intermediate-depth seismic source is conducted in this research. Two ground motion prediction models recommended by previous evaluations (Vacareanu et al. in Bull Earthq Eng 11(6):1867–1884, 2013a; Pavel et al. in Earthq Struct 6(1):1–18, 2014), as well as two new state-of-the-art ground motion prediction equations (Vacareanu et al. in J Earthq Eng, 2013b; Earthq Struct 6(2):141–161, 2014) are tested using an increased strong ground motion database consisting of 150 recordings from Vrancea subcrustal earthquakes. The evaluation is performed by using several goodness-of-fit parameters from the literature. Moreover, the applicability of the single-station sigma method is also investigated by using the same strong ground motion database recorded in 30 seismic stations from southern and eastern Romania. The influence of the soil conditions on the numerical results obtained in this study is investigated and discussed using the results provided by the analysis of variance method. The impact of the single-station standard deviation on the levels of seismic hazard is also assessed in this study, and the results show, in the analyzed cases, significant reductions of the hazard levels.     

The Use of Rock Mass Classification Systems to Estimate the Modulus and Strength of Jointed Rock

Three-dimensional, elastic and elasto-plastic finite element (FE) programs have permitted calculation of the displacements and the factor of safety (FOS) for the excavation for a tower, 132.70 m high (above foundation) on the island of Tenerife. The tower is supported by a 2 m thick reinforced concrete slab on jointed, vesicular and weathered basalt and scoria. The installation of rod extensometers at different depths below the slab has permitted comparison between measured and calculated displacements and the estimation of in situ deformation modulus. The moduli deduced from the simple empirical equations proposed by Hoek et al. (In: NARMS-TAC, 2002) and Gokceoglu et al. (Int J Rock Mech Min Sci 40:701–710, 2003) as a function of GSI, and Nicholson and Bieniawski (Int J Min Geol Eng 8:181–202, 1990) as a function of RMR, provide an acceptable fit with the measured settlements in this type of rock. Good correlation is also obtained with the empirical equation presented by Verman et al. (Rock Mech Rock Eng 30(3):121–127, 1997) that incorporates the influence of confining stress in the deformation modulus. The FOS obtained from different correlations with geomechanical classifications is within a relatively narrow range. These results increase our confidence in the use of classification schemes to estimate the deformation and stability in jointed rock.     

Indirect economic losses of drought under future projections of climate change: a case study for Spain

This study presents the results of numerical simulations of the 2004 Indian Ocean earthquake and tsunami in the Bay of Lhok Nga (northwestern coast of Sumatra, Indonesia) integrating sediment erosion and deposition. We investigate the transport of sediment both by suspension and by bedload under different scenarii of long breaking dispersive waves through a series of numerical experiments. The earthquake source model used by Koshimura et al. (Coast Eng J 51:243–273, 2008) with a 25-m dislocation better reproduces the wave travel time, flow depth and inundation area than the other models tested. The model reproduces realistically the pronounced coastal retreat in the northern part of Lhok Nga Bay (retreat ranging between 50 and 150 m), where Paris et al. (Geomorphology 104:59–72, 2009) estimated a mean retreat of 80 m. There is also a good agreement between the simulated area of coastal retreat (195,400 m²) and the field observations (203,200 m²). The simulation may underestimate the volume of tsunami deposits (611,700 m³ vs. 500,000–1,000,000 m³ estimated by Paris et al. (2009). The model fully reproduces the observed thickness of tsunami deposits when considering both bedload and suspension, even if bedload transport dominates. Limitations are due to micro-scale topographic, anthropic features (which are not always represented by the DEM) and the amount of debris which may influence flow dynamics and sediment transport.     

Oxygen fugacity control in piston-cylinder experiments: a re-evaluation

Jakobsson (Contrib Miner Petrol 164(3):397–407, 2012) investigated a double capsule assembly for use in piston-cylinder experiments that would allow hydrous, high-temperature, and high-pressure experiments to be conducted under controlled oxygen fugacity conditions. Using a platinum outer capsule containing a metal oxide oxygen buffer (Ni–NiO or Co–CoO) and H₂O, with an inner gold–palladium capsule containing hydrous melt, this study was able to compare the oxygen fugacity imposed by the outer capsule oxygen buffer with an oxygen fugacity estimated by the AuPdFe ternary system calibrated by Barr and Grove (Contrib Miner Petrol 160(5):631–643, 2010). H₂O loss or gain, as well as iron loss to the capsule walls and carbon contamination, is often observed in piston-cylinder experiments and often go unexplained. Only a few have attempted to actually quantify various aspects of these changes (Brooker et al. in Am Miner 83(9–10):985–994, 1998; Truckenbrodt and Johannes in Am Miner 84:1333–1335, 1999). It was one of the goals of Jakobsson (Contrib Miner Petrol 164(3):397–407, 2012) to address these issues by using and testing the AuPdFe solution model of Barr and Grove (Contrib Miner Petrol 160(5):631–643, 2010), as well as to constrain the oxygen fugacity of the inner capsule. The oxygen fugacities of the analyzed melts were assumed to be equal to those of the solid Ni–NiO and Co–CoO buffers, which is incorrect since the melts are all undersaturated in H₂O and the oxygen fugacities should therefore be lower than that of the buffer by 2 log $a_{{{\text{H}}_{ 2} {\text{O}}}}$ .     

Flow rule in a high-cycle accumulation model backed by cyclic test data of 22 sands

The flow rule used in the high-cycle accumulation (HCA) model proposed by Niemunis et al. (Comput Geotech 32: 245, 2005) is examined on the basis of the data from approximately 350 drained long-term cyclic triaxial tests (N = 10⁵ cycles) performed on 22 different grain-size distribution curves of a clean quartz sand. In accordance with (Wichtmann et al. in Acta Geotechnica 1: 59, 2006), for all tested materials, the “high-cyclic flow rule (HCFR)”, i.e., the ratio of the volumetric and deviatoric strain accumulation rates \(\dot{\varepsilon}_{\rm{v}}^{{\rm acc}}/\dot{\varepsilon}_{\rm{q}}^{{\rm acc}}\) , was found dependent primarily on the average stress ratio η ^av = q ^av/p ^av and independent of amplitude, soil density and average mean pressure. The experimental HCFR can be fairly well approximated by the flow rule of the modified Cam-clay (MCC) model. Instead of the critical friction angle \(\varphi_{\rm{c}}\) which enters the flow rule for monotonic loading, the HCA model uses the MCC flow rule expression with a slightly different parameter \(\varphi_{\rm{cc}}\) . It should be determined from cyclic tests. \(\varphi_{\rm{cc}}\) and \(\varphi_{\rm{c}}\) are of similar magnitude but not always identical, because they are calibrated from different types of tests. For a simplified calibration in the absence of cyclic test data, \(\varphi_{\rm{cc}}\) may be estimated from the angle of repose \(\varphi_{\rm{r}}\) determined from a pluviated cone of sand (Wichtmann et al. in Acta Geotechnica 1: 59, 2006). However, the paper demonstrates that the MCC flow rule with \(\varphi_{\rm{r}}\) does not fit well the experimentally observed HCFR in the case of coarse or well-graded sands. For an improved simplified calibration procedure, correlations between \(\varphi_{\rm{cc}}\) and parameters of the grain-size distribution curve (d ₅₀,   C _u) have been developed on the basis of the present data set. The approximation of the experimental HCFR by the generalized flow rule equations proposed in (Wichtmann et al. in J Geotech Geoenviron Eng ASCE 136: 728, 2010), considering anisotropy, is also discussed in the paper.     

Discussion of “The Bushveld Complex,South Africa: formation of platinum–palladium,chrome- and vanadium-rich layers via hydrodynamic sorting of a mobilized cumulate slurry in a large,relatively slowly cooling,subsiding magma chamber” by Maier et al. (2013) Miner Deposita 48:1–56

We believe the hypothesis presented by Maier et al. (Miner Deposita 48:1–56, 2012) for the formation of the various ore bodies in the Bushveld Complex to be overly simplistic, and we raise concerns that some of our work, used in support of this hypothesis, has been misrepresented. The formation of both diverse metalliferous layers (platinum-group element (PGE) reefs and Ti-magnetite layers) and some discordant (pipe) ore deposits has been ascribed by Maier et al. to the single unifying process of hydrodynamic sorting. The problem faced by authors of universal hypotheses for the Bushveld Complex is the sheer size and complexity of the intrusion. We disagree with many aspects of the overall Maier et al. model and have also identified several minor errors on maps and photographs, although some of these do not have a material effect on the model. The nature and origin of the layering is, however, too complex a topic to deal with in the context of this commentary, and we restrict ourselves to noting that our preferred hypothesis, namely the incremental buildup of layering from numerous episodes of replenishment, by different magma lineages, is consistent with field relationships. Our hypothesis for the origin of the ultramafic-hosted PGE-rich reefs, i.e., lateral mixing, is applicable to economically mineralized reefs (Mitchell and Scoon, Econ Geol 102:971–1009, 2007) and poorly mineralized layers such as the Pseudoreef harzburgite (Scoon and De Klerk, Canad Mineral 25:51–77, 1987) and the chromitite layers below the UG2 (Scoon and Teigler, Econ Geol 89:1094–1121, 1994).     

Assessment of Liquefaction Potential of Guwahati City: A Case Study

The liquefaction potential of saturated cohesionless deposits in Guwahati city, Assam, was evaluated. The critical cyclic stress ratio required to cause liquefaction and the cyclic stress ratio induced by an earthquake were obtained using the simplified empirical method developed by Seed and Idriss (J soil Mech Found Eng ASCE 97(SM9):1249–1273, 1971, Ground motions and soil liquefaction during earthquakes. Earthquake Engineering Research Institute, Berkeley, CA, 1982) and Seed et al. (J Geotech Eng ASCE 109(3):458–483, 1983, J Geotech Eng ASCE 111(12):1425–1445, 1985) and the Idriss and Boulanger (2004) method. Critical cyclic stress ratio was based on the empirical relationship between standard penetration resistance and cyclic stress ratio. The liquefaction potential was evaluated by determining factor of safety against liquefaction with depth for areas in the city. A soil database from 200 boreholes covering an area of 262 km² was used for the purpose. A design peak ground acceleration of 0.36 g was used since Guwahati falls in zone V according to the seismic zoning map of India. The results show that 48 sites in Guwahati are vulnerable to liquefaction according to the Seed and Idriss method and 49 sites are vulnerable to liquefaction according to the Idriss and Boulanger method. Results are presented as maps showing zones of levels of risk of liquefaction.     

Chromite alteration processes within Vourinos ophiolite

The renewed interest in chromite ore deposits is directly related to the increase in Cr price ruled by international market trends. Chromite, an accessory mineral in peridotites, is considered to be a petrogenetic indicator because its composition reflects the degree of partial melting that the mantle experienced while producing the chromium spinel-bearing rock (Burkhard in Geochim Cosmochim Acta 57:1297–1306, 1993). However, the understanding of chromite alteration and metamorphic modification is still controversial (e.g. Evans and Frost in Geochim Cosmochim Acta 39:959–972, 1975; Burkhard in Geochim Cosmochim Acta 57:1297–1306, 1993; Oze et al. in Am J Sci 304:67–101, 2004). Metamorphic alteration leads to major changes in chromite chemistry and to the growth of secondary phases such as ferritchromite and chlorite. In this study, we investigate the Vourinos complex chromitites (from the mines of Rizo, Aetoraches, Xerolivado and Potamia) with respect to textural and chemical analyses in order to highlight the most important trend of alteration related to chromite transformation. The present study has been partially funded by the Aliakmon project in collaboration between the Public Power Corporation of Greece and Institute of Geology and Mineral Exploration of Kozani.     

Melting phase relations of a mica–clinopyroxenite from the Milk River area, southern Alberta, Canada

Melting experiments were conducted on a mica–clinopyroxenite xenolith brought up in a minette dyke in southern Alberta, Canada, near Milk River. Both the minettes and mica–clinopyroxenite xenoliths were studied by Buhlmann et al. (Can J Earth Sci 37:1629–1650, 2000), who hypothesized that the minettes formed by partial melting of a mantle source containing clinopyroxene + phlogopite ± olivine, at pressures ≥1.7 GPa. In liquidus experiments performed on the most primitive minette in our previous study (Funk and Luth in Contrib Mineral Petrol 164:999–1009, 2012), we found a multiple saturation point where olivine and orthopyroxene coexisted with liquid at 1.77 GPa and 1,350 °C. We argued that the minette originally formed by partial melting of clinopyroxene + phlogopite, but had re-equilibrated with a harzburgite during ascent. In the current study, we wanted to test both the source region hypothesis of Buhlmann et al. and our re-equilibration hypothesis by studying the near-solidus phase equilibria of a mica + clinopyroxene assemblage. We found the solidus for our xenolith has a steep slope in P–T space and lies at temperatures above those of a normal cratonic geotherm, implying that this mica–clinopyroxenite is stable in the cratonic mantle. Melting could occur at greater depths, where the solidus is extrapolated to cross the geotherm or must be induced either by raising the temperatures of the surrounding rocks or by introducing hydrous fluids into the source. Our melts are in equilibrium with clinopyroxene and olivine. The compositions of the liquids derived from melting this xenolith are similar to madupitic lamproites from the Leucite Hills, Wyoming, studied by Carmichael (Contrib Mineral Petrol 15:24–66, 1967) and Barton and Hamilton (Contrib Mineral Petrol 66:41–49, 1978; Contrib Mineral Petrol 69:133–142, 1979). Barton and Hamilton (Contrib Mineral Petrol 69:133–142, 1979) proposed that the madupitic lamproites may have come from a source containing mica and pyroxene. This study supports their hypothesis. The composition of the most primitive minette from southern Alberta lies between our experimental melt and a population of representative mantle orthopyroxenes. We conclude from our study that the Milk River minettes were likely derived from a source containing phlogopite, clinopyroxene and trace amounts of apatite, which formed olivine upon melting. During ascent, the melts changed composition by reacting with orthopyroxene.     

Applying neighbourhood classification systems to natural hazards: a case study of Mt Vesuvius

Mt Vesuvius is regarded as one of the most deadly volcanoes on earth. With over 1 million people living on its flanks and in its periphery, there is little doubt that an eruption of sub-Plinian magnitude would be catastrophic to the livelihood and well being of contemporary Neopolitans. Such a large scale eruption would have wide ranging and differential effects on the surrounding population. Whereas previous studies of social vulnerability have focused on individual demographic factors (such as age, income or ethnicity), this research proposes the application of a general neighbourhood classification system to assess natural hazard vulnerability. In this study, Experian’s Mosaic Italy is used to classify and delineate the most vulnerable neighbourhood types around the province of Naples. Among the neighbourhoods considered most at risk, those areas with high proportions of elderly and low income families are deemed particularly vulnerable. With current evacuation plans deemed outdated and poorly communicated to the locals Rolandi (2010), Barberi et al. (2008), this methodology could prove to be a useful input to both town planners and civil protection agencies. A range of statistical measures and geophysical risk boundaries are employed here to assess the different areas of human resilience.     

Catchment-wide estimate of single storm interrill soil erosion using an aggregate instability index: a model based on geographic information systems

The main objective of this paper is to estimate interrill erosion after rainfall in the basin of Mourganis river (442?km²; Kalabaka province, Trikala prefecture, Thessaly, Greece). For the estimation of the interrill erosion, the method of Valmis et al. (1988) was used, in combination with Nearing et al. (1989). Input data of the algorithm include the slope angle of the ground surface, the rainfall, the ground cover type, the height of canopy, and the instability of ground of the study area. The spatial data were processed by standard GIS software. Soil samples were collected in the field to calibrate the model. The results comprise soil erosion maps for two specific rainfall scenarios. The first rainfall scenario refers to the most extreme rainfall in this catchment that happened on the 7/21/1959 with 48?mm/h. The second scenario is closer to average as the intensity rainfall is 3.54?mm/h. The total mass of eroded material ranges from 0.048?t/ha (assuming mean rainfall intensity) up to 3.5?t/ha (for the extreme scenario). We note that the western part of the Mourgani basin exhibits higher erosion than the eastern part.     

Evaluating the Poroelastic Effect on Anisotropic, Organic-Rich, Mudstone Systems

Understanding the poroelastic effect on anisotropic organic-rich mudstones is of high interest and value for evaluating coupled effects of rock deformation and pore pressure, during drilling, completion and production operations in the oilfield. These applications include modeling and prevention of time-dependent wellbore failure, improved predictions of fracture initiation during hydraulic fracturing operations (Suarez-Rivera et al. Presented at the Canadian Unconventional Resources Conference held in Calgary, Alberta, Canada, 15–17 November 2011. CSUG/SPE 146998 2011), improved understanding of the evolution of pore pressure during basin development, including subsidence and uplift, and the equilibrated effective in situ stress (Charlez, Rock mechanics, vol 2 1997; Katahara and Corrigan, Pressure regimes in sedimentary basins and their prediction: AAPG Memoir, vol 76, pp 73–78 2002; Fjær et al. Petroleum related rock mechanics. 2nd edn 2008). In isotropic rocks, the coupled poro-elastic deformations of the solid framework and the pore fluids are controlled by the Biot and Skempton coefficients. These are the two fundamental properties that relate the rock framework and fluid compressibility and define the magnitude of the poroelastic effect. In transversely isotropic rocks, one desires to understand the variability of these coefficients along the directions parallel and longitudinal to the principal directions of material symmetry (usually the direction of bedding). These types of measurements are complex and uncommon in low-porosity rocks, and particularly problematic and scarce in tight shales. In this paper, we discuss a methodology for evaluating the Biot’s coefficient, its variability along the directions parallel and perpendicular to bedding as a function of stress, and the homogenized Skempton coefficient, also as a function of stress. We also predict the pore pressure change that results during undrained compression. Most importantly, we provide values of transverse and longitudinal Biot’s coefficients and the homogenized Skempton coefficient for two important North American, gas-producing, organic-rich mudstones. These results could be used for petroleum-related applications.     

Earthquake geology of Kashmir Basin and its implications for future large earthquakes

Two major traces of active thrust faults were identified in the Kashmir Basin (KB) using satellite images and by mapping active geomorphic features. The ~N130°E strike of the mapped thrust faults is consistent with the regional ~NE–SW convergence along the Indian–Eurasian collision zone. The ~NE dipping thrust faults have uplifted the young alluvial fan surfaces at the SW side of the KB. This created a major tectono-geomorphic boundary along the entire strike length of the KB that is characterised by (1) a low relief with sediment-filled sluggish streams to the SE and (2) an uplifted region, with actively flowing streams to the SW. The overall tectono-geomorphic expression suggests that recent activity along these faults has tilted the entire Kashmir valley towards NE. Further, the Mw 7.6 earthquake, which struck Northern Pakistan and Kashmir on 8 October 2005, also suggests a similar strike and NE dipping fault plane, which could indicate that the KB fault is continuous over a distance of ~210 km and connects on the west with the Balakot Bagh fault. However, the geomorphic and the structural evidences of such a structure are not very apparent on the north-west, which thus suggest that it is not a contiguous structure with the Balakot Bagh fault. Therefore, it is more likely that the KB fault is an independent thrust, a possible ramp on the Main Himalayan Thrust, which has uplifting the SW portion of the KB and drowning everything to the NE (e.g. Madden et al. 2011). Furthermore, it seems very likely that the KB fault could be a right stepping segment of the Balakot Bagh fault, similar to Riasi Thrust, as proposed by Thakur et al. (2010). The earthquake magnitude is measured by estimating the fault rupture parameters (e.g. Wells and Coppersmith in Bull Seismol Soc Am 84:974–1002, 1994). Therefore, the total strike length of the mapped KB fault is ~120 km and by assuming a dip of 29° (Avouac et al. in Earth Planet Sci Lett 249:514–528, 2006) and a down-dip limit of 20 km, a Mw of 7.6 is possible on this fault.     

EPR study of chromium-doped forsterite crystals: Cr3+(M1) with associated trivalent ions Al3+ and Sc3+

Electron paramagnetic resonance (EPR) study of single crystals of forsterite co-doped with chromium and scandium has revealed, apart from the known paramagnetic centers Cr³⁺(M1) and Cr³⁺(M1)– $ V_{{{\text{Mg}}^{2 + } }} $ (M2) (Ryabov in Phys Chem Miner 38:177–184, 2011), a new center Cr³⁺(M1)– $ V_{{{\text{Mg}}^{2 + } }} $ (M2)–Sc³⁺ formed by a Cr³⁺ ion substituting for Mg²⁺ at the M1 structural position with a nearest-neighbor Mg²⁺ vacancy at the M2 position and a Sc³⁺ ion presumably at the nearest-neighbor M1 position. For this center, the conventional zero-field splitting parameters D and E and the principal g values have been determined as follows: D?=?33,172(29) MHz, E?=?8,482(13) MHz, g?=?[1.9808(2), 1.9778(2), 1.9739(2)]. The center has been compared with the known ion pair Cr³⁺(M1)–Al³⁺ (Bershov et al. in Phys Chem Miner 9:95–101, 1983), for which the refined EPR data have been obtained. Based on these data, the known sharp M1″ line at 13,967?cm^?1 (with the splitting of 1.8?cm^?1), observed in low-temperature luminescence spectra of chromium-doped forsterite crystals (Glynn et al. in J Lumin 48, 49:541–544, 1991), has been ascribed to the Cr³⁺(M1)–Al³⁺ center. It has been found that the concentration of the new center increases from 0 up to 4.4?×?10¹⁵?mg^?1, whereas that of the Cr³⁺(M1) and Cr³⁺(M1)– $ V_{{{\text{Mg}}^{2 + } }} $ (M2) centers quickly decreases from 7.4?×?10¹⁵?mg^?1 down to 3?×?10¹⁵?mg^?1 and from 2.7?×?10¹⁵?mg^?1 down to 0.5?×?10¹⁵?mg^?1, i.e., by a factor of 2.5 and 5.4, respectively, with an increase of the Sc content from 0 up to 0.22 wt?% (at the same Cr content 0.25 wt?%) in the melt. When the Sc content exceeds that of Cr, the concentration of the new center decreases most likely due to the formation of the Sc³⁺(M1)– $ V_{{{\text{Mg}}^{2 + } }} $ (M2)–Sc³⁺ complex instead of the Cr³⁺(M1)– $ V_{{{\text{Mg}}^{2 + } }} $ (M2)–Sc³⁺ center. The formation of such ordered neutral complex is in agreement with the experimental results, concerning the incorporation of Sc into olivine, recently obtained by Grant and Wood (Geochim Cosmochim Acta 74:2412–2428, 2010).