Wave characteristic distributions for Gaussian waves—Wave-length, amplitude and steepness

In as tationary stochastic process the wave-length and amplitude are defined as the difference in time and height between a crest and the following trough. The distributions of these quantities are of great practical importance, but no closed form expressions are known at present. In previous papers we have presented an approximation which gives correct upper and lower bounds, regardless of the covariance structure under Gaussian assumptions. In this paper the suggested approximations are compared to two simpler approximations, one due to Cavanié et al. (1976) based on a cosine process and a new one, derived by replacing the model process by its regression curve.     

Climatic intrannual variability of the geostrophic circulation of the main Black Sea current

A quasi-periodic (wave) spatial-temporal structure of the intrannual variability of the climatic fields of the seawater geostrophic motion within the constant halocline in the Black Sea (75–300m) has been revealed on the basis of generalized archival data on hydrological observations in the main Black Sea current (MBSC) near the Crimea and Caucasus. The variability with annual and semi-annual periods has the character of standing quasi-geostrophic waves at 2- to 4-month periods which become progressive as the direction of their propagation changes during the year. The energy characteristics for the forms of variability revealed are discussed and interpreted from the viewpoint of gradient-eddy waves and the hydrodynamic instability of the MBSC.Translated by Mikhail M. Trufanov.     

Pacific walruses, indigenous hunters, and climate change: Bridging scientific and indigenous knowledge

This paper presents and evaluates two perspectives on changing climate–walrus–human relationships in the Beringian region, from the viewpoints of marine biology and ecology, and from that of indigenous hunters. Bridging these types of knowledge is vital in order to grasp the complexity of the processes involved and for advancing understanding of subarctic marine ecosystems that are currently experiencing rapid ecological and social change. We argue that despite substantial gaps and distinctions, information generated by scientists and indigenous hunters have many similarities. Differences in interpretation are primarily due to scaling and temporal rates of change of knowledge, which could be rectified through more active sharing of expertise and records, enhanced documentation of indigenous observations, more collaborative research, and increased insight from the social sciences.     

Note on the intensity of encountered waves

An apparent wave is a part of the sea record observed between two successive upcrossings of the still water level. Integral formulas are given for intensities of encountered waves that overtake a ship sailing in directional sea with constant velocity. The formulas can be evaluated exactly in the case when the directional spectrum is known and the sea is assumed to be Gaussian, i.e. is a sum of noninteracting sinusoidal waves.     

Osmium isotope and highly siderophile element systematics of lunar impact melt breccias: Implications for the late accretion history of the Moon and Earth

To characterize the compositions of materials accreted to the Earth-Moon system between about 4.5 and 3.8 Ga, we have determined Os isotopic compositions and some highly siderophile element (HSE: Re, Os, Ir, Ru, Pt, and Pd) abundances in 48 subsamples of six lunar breccias. These are: Apollo 17 poikilitic melt breccias 72395 and 76215; Apollo 17 aphanitic melt breccias 73215 and 73255; Apollo 14 polymict breccia 14321; and lunar meteorite NWA482, a crystallized impact melt. Plots of Ir versus other HSE define excellent linear correlations, indicating that all data sets likely represent dominantly two-component mixtures of a low-HSE target, presumably endogenous component, and a high-HSE, presumably exogenous component. Linear regressions of these trends yield intercepts that are statistically indistinguishable from zero for all HSE, except for Ru and Pd in two samples. The slopes of the linear regressions are insensitive to target rock contributions of Ru and Pd of the magnitude observed; thus, the trendline slopes approximate the elemental ratios present in the impactor components contributed to these rocks. The ¹⁸⁷Os/¹⁸⁸Os and regression-derived elemental ratios for the Apollo 17 aphanitic melt breccias and the lunar meteorite indicate that the impactor components in these samples have close affinities to chondritic meteorites. The HSE in the Apollo 17 aphanitic melt breccias, however, might partially or entirely reflect the HSE characteristics of HSE-rich granulitic breccia clasts that were incorporated in the impact melt at the time of its creation. In this case, the HSE characteristics of these rocks may reflect those of an impactor that predated the impact event that led to the creation of the melt breccias. The impactor components in the Apollo 17 poikilitic melt breccias and in the Apollo 14 breccia have higher ¹⁸⁷Os/¹⁸⁸Os, Pt/Ir, and Ru/Ir and lower Os/Ir than most chondrites. These compositions suggest that the impactors they represent were chemically distinct from known chondrite types, and possibly represent a type of primitive material not currently delivered to Earth as meteorites.     

Geometry of the fault zone of the 2003 Ms = 7.5 Chuya earthquake and associated stress fields, Gorny Altai

The co-seismic deformations produced during the September 27, 2003 Chuya earthquake (Ms = 7.5) that affected the Gorny Altai, Russia, are described and discussed along a 30 km long segment. The co-seismic deformations have manifested themselves both in unconsolidated sediments as R- and R′-shears, extension fractures and contraction structures, and in bedrock as the reactivation of preexisting schistosity zones and individual fractures, as well as development of new ruptures and coarse crushing zones. It has been established that the pattern of earthquake ruptures represents a typical fault zone trending NW–SE with a width reaching 4–5 km and a dextral strike–slip kinematics. The initial stress field that produced the whole structural pattern of co-seismic deformations during the Chuya earthquake, is associated with a transcurrent regime with a NNW–SSE, almost N–S, trending of compressional stress axis (σ₁), and a ENE–WSW, almost E–W, trending of tensional stress axis (σ₃). The state of stress in the newly-formed fault zone is relatively uniform. The local stress variations are expressed in insignificant deviation of σ₁ from N–S to NW–SE or NE–SW, in short-term fluctuations of relative stress values in keeping their spatial orientations, or in a local increase of the plunge angle of the σ₁. The geometry of the fault zone associated with the Chuya earthquake has been compared with the mechanical model of fracturing in large continental fault zones with dextral strike–slip kinematics. It is apparent that the observed fracture pattern corresponds to the late disjunctive stage of faulting when the master fault is not fully developed but its segments are already clearly defined. It has been shown that fracturing in widely different rocks follows the common laws of the deformation of solid bodies, even close to the Earth surface, and with high rates of movements.     

3D seismic analysis of the Coast Shear Zone in SE Alaska and Western British Columbia: Broadside analysis of ACCRETE wide-angle data

The multidisciplinary ACCRETE project addresses the question of continental assemblage in southeast Alaska and western British Columbia by terrane accretion and magmatic addition. The previous studies of this project yielded important information for understanding the structures across the Coast Shear Zone (CSZ) and the formation of the CSZ and the Coast Mountains Batholith (CMB). The present study extends these interpretations into pseudo-3-D by using two additional wide-angle ACCRETE seismic lines. By analyzing the broadside wide-angle data using a series of laterally homogeneous 2-D models, we derive a lower-resolution 3-D velocity model of the outboard terranes and constrain variations in crustal thickness across and along the CSZ. Models of the broadside data confirms major structural and compositional trends extend along strike to the northwest. The key features are: a) a steep Moho ramp only  15-km wide is coincident with the CSZ and divides thin (25 ± 1 km) crust to the west below the west-vergent thrust belt (WTB) from thicker ( 31 ± 1 km) crust to the east below the CMB, (b) low-velocity mantle (7.7--7.9 km/s) extends beneath the entire study region indicating high crustal and upper-mantle temperatures below the WTB and CMB, and (c) the Alexander terrane is characterized by strong mid-crustal reflectivity and high lower crustal velocities that are consistent with gabbroic composition. This study extends the earlier interpretation and implies that the ramp is indeed likely associated with transpressional tectonics and magmatic crustal addition east of the CSZ.     

Fatal landslides in Europe

Landslides are a major hazard causing human and large economic losses worldwide. However, the quantification of fatalities and casualties is highly underestimated and incomplete, thus, the estimation of landslide risk is rather ambitious. Hence, a spatio-temporal distribution of deadly landslides is presented for 27 European countries over the last 20  years (1995–2014). Catastrophic landslides are widely distributed throughout Europe, however, with a great concentration in mountainous areas. In the studied period, a total of 1370 deaths and 784 injuries were reported resulting from 476 landslides. Turkey showed the highest fatalities with 335. An increasing trend of fatal landslides is observed, with a pronounced number of fatalities in the latest period from 2008 to 2014. The latter are mostly triggered by natural extreme events such as storms (i.e., heavy rainfall), earthquakes, and floods and only minor by human activities, such as mining and excavation works. Average economic loss per year in Europe is approximately 4.7 billion Euros. This study serves as baseline information for further risk mapping by integrating deadly landslide locations, local land use data, and will therefore help countries to protect human lives and property.     

Magnetic variations excited by a radial magnetic dipole located in the earth's core

Summary Theoretical formulae are derived for computing a variable magnetic field, excited by a harmonically oscillating radial magnetic dipole (RMD), located eccentrically at the surface of the Earth's core. By numerical computations, using a three-layered conductivity model of the Earth, it is proved that the field due to this source, computed for the surface of the Earth, is relatively weak in comparison to the field of a stationary magnetic dipole, provided the period of the changes is less than 500 years. The zone of influence of the RMD at the Earth's surface is also determined and on its basis a number of conclusions were drawn with respect to representing the non-dipole part of the geomagnetic field by means of the RMD system in the Earth's core.Dedicated to RNDr. Jan Pícha, CSc., on his 60th Birthday     

Geochronology and excess Ar geochemistry of the Lhotse Nup leucogranite, Nepal Himalaya

⁴⁰Ar/³⁹Ar dating experiments on several coexisting minerals from two close-by leucogranite outcrops near Lhotse Nup glacier (Nepal Himalaya) reveal a complex behaviour. Four biotite and muscovite ages cluster around 15.5 Ma, a lower value than literature Rb/Sr ages on splits of the same four micas, suggesting a discrepancy with the ideal cooling age sequence observed in the Alps.A strongly discordant Ar-Ar spectrum on tourmaline does not allow a chronological interpretation.A potassium feldspar shows a slow-cooling staircase spectrum with a superimposed saddle diagnostic of excess Ar. HF leaching removed excess Ar but caused great perturbations to the minimum step ages, isochron plots, and the release of reactor-produced Ar isotopes. The present data require that the currently fashionable interpretations of feldspar systematics be radically changed.The main chronological conclusions rely on the eight mica ages. Their decrease from 18.2 to 15.3 Ma dates the cooling of the Lhotse Nup leucogranite.