The possibility of jointly inverting the receiver function waveforms and the seismic noise horizontal-to-vertical spectral ratio to study the Earth’s structure is substantiated. Both data types are widely used for constructing a velocity model beneath a single seismic station. The main difference between the methods is associated with the different frequency content of input data which is 0.02–0.2 Hz in receiver functions and 0.5–20 Hz in seismic noise. It is shown that notwithstanding these differences, the joint inversion approach more effectively reconstructs the model of the medium in case when a station is underlain by a complexly structured sedimentary cover. In the practical implementation, the parameters of both seismic methods are described in a flat-layer representation of the medium. Besides, both methods are most sensitive to the depth distribution of S -wave velocities. In this work, we use records from the Monakovo seismic station, Nizhny Novgorod region, Russia, to construct a model of the medium consistent with both data types. It is shown that the allowance for the H / V spectral curve in the receiver function interpretation provides additional constraints on the small-scale structure of the upper part of the velocity section thus stabilizing the reconstruction procedure.

Simultaneous inversion of P and S receiver functions and of dispersion curves of Rayleigh waves for 16 seismograph stations provides insight into structure beneath the Caucasus and the Caspian Basin up to a depth of 700 km. Crustal thickness of the Caucasus ranges from 30 to 50 km. An anomalously high velocity ratio of the P and S waves (2.0 and more) is observed systematically in the upper crust. The upper mantle at most locations can be split into the upper high S wave velocity layer (4.5–4.8 km/s, litospheric mantle) and the underlying low S velocity (4.0–4.2 km/s) asthenosphere. The depth to the lithosphere—asthenosphere boundary (LAB) ranges from 90 to 145 km. Under the East Caucasus the depth to the 410 km boundary is close to the standard (IASP91) value, whereas the 660 km boundary is lowered on the average by 10 km. The sinking of the 660 km boundary may be caused by cooling and/or hydration of the lower transition zone by the subducted Neo-Tethys plate. Under the western margin of the Caspian Basin structure of the upper mantle resembles a subduction zone: the low-velocity ( Vs < 4.2 km/s) asthenosphere which lies immediately beneath the Moho boundary is underlain at a depth of 140 km by a layer of (subducted) high-velocity lithosphere. The S wave receiver functions indicate that the 410 km boundary beneath the Caspian Basin is lowered by about 10 km. This may be an effect of elevated by 100°C temperature. An uplift of the 410 km boundary is found beneath the Scythian platform.

The results of studying the deep structure of the Earth’s crust and upper mantle in the central part of the Russian platform from receiver functions are presented. The records of teleseismic waves by the Monakovo small-aperture seismic array in the region of the northwestern slope of the Tokmovskii Arch of the Volga–Kama anteclise are used. The modification of the P-receiver function method (Vinnik, 1977) suggested in (Sanina et al., 2014) for analyzing the receiver functions in the regions with a complexly structured upper part of the section and the presence of a thick sedimentary cover is applied. The method is based on separating the high- and low-frequency components of the seismic record and successive reconstruction of the V-s velocity section in the upper part of the crust, which is performed first and, next, the entire deep section of the crust and the mantle down to a depth of ~300 km. The positions of the seismic conversion boundaries in the crust and upper mantle beneath the Monakovo array are determined. The upper mantle velocity section constructed based on the observations at the Mikhnevo array (Sanina et al., 2014) is compared with the world data on the ancient Precambrian platform.

A deep-focus (H = 609 km) earthquake with Mw = 8.3 occurred in the Sea of Okhotsk on May 24, 2013. This earthquake was felt in Moscow at a distance of about 6500 km from the epicenter but barely felt on the western coast of Kamchatka, which is located within 200 km of the source. In this paper, an attempt is made to discover the probable causes of this phenomenon in the instrumental records of the earthquake. It is most probable that the anomalously high amplitudes in the group of SSS phases, which are observed in the vertical component, appear as the result of their superimposition on the surface waves. Different mechanisms can be suggested to interpret the formation of the observed wave pattern.

The P- and S -wave receiver functions and dispersion curves of the fundamental Rayleigh wave are used to study the lithosphere within the Central Anatolian Plateau. The results for eight broadband seismic stations are presented. It is established that within the plateau, the crust with a thickness of about 35 km is underlain by the mantle lid with its bottom at a depth of about 60 km. The velocities of longitudinal ( Vp ) and shear ( Vs ) waves in this layer are at most 7.6 and 4.5 km/s, respectively, and the Vp / Vs ratio is close to 1.7 (i.e., by 6% lower than in the standard IASP91 and PREM models). Such a low velocity ratio is characteristic of rocks having high orthopyroxene content. Beneath the high-velocity mantle lid, the S -wave velocity decreases to 4.0–4.2 km/s and the Vp / Vs ratio is close to its standard value (1.8). At most stations, the P -wave receiver functions do not contain seismic phase P 410 s , which is formed at the global seismic boundary at a depth of 410 km. The seismic boundary at a depth of 410 km is related to the olivine-spinel phase transformation, and its absence can indicate the anomalously low olivine content and high basalt content. This anomaly is probably associated with the subduction of a large amount of oceanic crust during the closure of the Tethys. The results of the study overall indicate the high informativity of the used method.

The SSD-3 three-channel seismic recorder and the ADSS-3 three-component broadband standalone digital seismic station based on the SSD-3 together with SM-3E seismic sensors were developed. The main advantage of this equipment in comparison with foreign and domestic analogs is simplicity and convenience while maintaining high technical characteristics. The structure and operation of the seismic sensor and seismic recorder are considered, and their main technical characteristics are given. Laboratory, bench, and comparative tests of the seismic recorder and station demonstrated their working capacity and compliance with the development goal. Based on the test results, the ADSS-3 seismic station was commissioned as a three-component broadband observation point of the Mikhnevo small-aperture seismic array. The data obtained using the ADSS-3 made is possible to study the structure of the crust and upper mantle of this region using the receiver function method.

We present a new Moho map for the Early-Proterozoic northwestern part of the Fennoscandian Shield, where the POLENET/LAPNET passive seismic array was located. The map is based on previously published and re-evaluated controlled source seismic data and P-wave receiver functions as well as new estimates of the Moho depth obtained by our analysis of P-wave receiver functions at broadband stations of the POLENET/LAPNET array. We estimated individual data quality for all input data and combined them into a new Moho map using CRUST3D software. The software seeks the simplest (smoothest) Moho surface that is consistent with all seismic data within their individual uncertainty limits. The new Moho map indicates that the crustal thickness in the study region varies between 42km and 58km, with the greatest thickness being reached in two separate areas in the northeast and the southeast. Two areas with relatively flat and shallow Moho, with an average Moho depth of c. 44km, are located in the eastern and south-western parts of the study area. These two areas are separated by the Moho depression, with a maximum depth of 58km. They can be associated with the Archean core of the Karelian craton and with the part of it that was reworked during the Early Proterozoic, respectively. A region with an average Moho depth of c. 47km can be seen in the northern part of our study area, deepening to c. 55km in the northeastern corner.

P and S receiver functions (PRFs and SRFs, respectively) for 21 broad-band seismograph stations of the India Meteorological Department (IMD) illuminate lithosphere and the underlying mantle of some previously poorly sampled regions of the Indian sub-continent. Our analysis demonstrates that the Archean and Early Proterozoic lithospheric keel of the Indian shield has been reworked by younger processes. We find very low S-wave velocities in the uppermost mantle (from 4.0 to 4.3 km/s) to the north of the Deccan Volcanic Province (Kutch region and Aravalli Craton) (1), in the south (Southern Granulite Terrain and Sri Lanka) (2) and in the north-east (Gangetic Plane, Bengal Basin and Singhbuhm Craton) (3). The anomalies 1 and 2 may extend into the transition zone. Early arrivals of the S410p seismic phase are indicative of anomalously high Vp/Vs ratio (~ 1.9) in the upper mantle of the low-velocity regions, whereas late arrivals in the western Himalaya, Ladakh and western Tibet are consistent with the previously found indications of anomalously low Vp/Vs ratio. A transition from the high-S-velocity mantle lid to a layer of slightly lower velocity is seen in part of the data but a straightforward interpretation of this transition as the lithosphere–asthenosphere boundary is problematic. A mafic S velocity in the upper crust and a pronounced low-S-velocity layer in the lower crust beneath the eruptive center is practically the only specific feature in the lithosphere that may be linked to the Deccan Traps. A separation in depths between the 410-km and 660-km discontinuities varies laterally in a range from 240 to 270 km. The largest uplift of the 410-km discontinuity (up to 390 km) is observed beneath the foothills of the Himalaya where it is caused by cooling of the transition zone by the ongoing continental collision.

Shear wave splitting in the seismic SKS phase provides a unique possibility to judge on deformations at depths inaccessible for direct observations. Fast S wave polarization direction in collisional belts is often parallel to the trend of the belt, although deformations of the mantle lithosphere in low-angle thrusts would lead to the fast polarization direction normal to the trend of the belt. These considerations suggested that the upper mantle in collisional belts is decoupled from the crust. However, SKS technique is notable by a poor depth resolution, and usually it assumes that the fast polarization direction is the same at any depth, which is hard to justify. Here, to investigate depth dependent azimuthal anisotropy in the mantle, we invert jointly P receiver functions and SKS particle motions at a number of seismograph stations. The technique involves azimuthal filtering of the receiver functions and provides a criterion to discriminate between the effects of azimuthal anisotropy and lateral heterogeneity of isotropic medium. A search for the optimum models is conducted with a technique similar to simulated annealing. Testing with synthetics demonstrates that this approach is robust. The results for 10 seismograph stations in the Tien Shan, the world's most active intracontinental collisional belt in Central Asia, reveal a pronounced change in the patterns of azimuthal anisotropy at a depth around 100 km. In the mantle lithosphere (at depths less than 100 km), anisotropy is relatively weak and fast wave polarization direction varies laterally in a broad range. This layer is not necessarily decoupled from the crust: its anisotropy can be a combined effect of present day thrusting and of deformations of the geologic past. In the lower layer (asthenosphere) the average azimuth of fast wave polarization is close to the trend of the belt, whereas magnitude of S wave anisotropy is stable and large (between 5 and 6 per cent). This anisotropy is a likely result of recent uniaxial shortening at right angle to the trend of the belt. At some stations the data require anisotropy in the crust. There is no evidence for anisotropy at depths exceeding 150-250 km.

A 3-D velocity model of the Tien Shan crust and upper mantle is constructed through the inversion of the receiver functions of P and S waves together with teleseismic traveltime anomalies at nearly 40 local seismic stations. It is found that in the vast central region, where no strong earthquakes have been known over the past century, the S wave velocity at depths of 10–35 km is lower than in adjacent regions by up to 10%. These data are evidence for mechanical weakness of the crust preventing the accumulation of elastic energy. Apparently, the lower velocity and the weakness of the crust are due to the presence of water. The weakness of the crust is one of the possible reasons for the strain localization responsible for the formation of the present Tien Shan but can also be due in part to the young orogenesis. The crustal thickness is largest (about 60 km) in the Tarim-Tien Shan junction zone. The crust-mantle boundary in this region descends by a jump as a result of an increase in the lower crust thickness. This is probably due to the underthrusting of the Tien Shan by the Tarim lithosphere. This causes the mechanically weak lower crust of the Tarim to delaminate and accumulate in nearly the same way as an accretionary prism during the subduction of oceanic lithosphere. In the upper mantle, the analysis has revealed a low velocity anomaly, apparently related to basaltic outflows of the Upper Cretaceous-Early Paleogene. The Cenozoic Bachu uplift in the northern Tarim depression is also associated with the low velocity anomaly. The Naryn depression is characterized by a high velocity in the upper mantle and can be interpreted as a fragment of an ancient platform.

[1] Based on data of three three-component seismographs belonging to the temporary small-aperture Russian Karelia Seismic Array (RUKSA) in the Petrozavodsk region (Karelia), a 1-D velocity model of the crust is constructed by the method of the receiver function. Waveforms of distant earthquakes recorded by short-period instruments with improved characteristics are used. The data were inverted by the simulated annealing method. The inversion was stabilized by using phase velocities of Rayleigh waves and traveltimes of converted Ps waves from the 410-km boundary determined from broadband records of the SVEKALAPKO seismic array. Anomalously low seismic velocities are discovered in the upper part of the cross section beneath the RUKSA array.

To obtain an image of the deep structure of the Tien Shan in central Asia, we invert P and S receiver functions jointly for almost 40 local broad-band seismograph stations. The inversion is performed using a simulated annealing technique. The combined inversion is an improvement on earlier studies, where P and S receiver functions were inverted separately. Using this approach, we deal with structural imaging problems that are usually investigated with teleseismic body wave and surface wave tomography techniques. We demonstrate that the uppermost mantle in the north of the central Tien Shan is composed of a high-velocity lid a few tens of kilometers thick above a pronounced low-velocity zone. The crustal structure in this region provides evidence of magmatic underplating. These features are likely related to a small plume that is manifested by basaltic eruptions of Cretaceous–Paleogene age. The low-velocity layer is also found in a southeast trending corridor, which may correspond to the Bachu uplift in the Tarim basin. Crustal thickness beneath the orogen varies from about 45 to about 70 km. The smallest values, most likely inherited from the pre-orogenic era, are found in a neighborhood of the Talas–Fergana fault. Similar values are characteristic of the Kazakh shield in the north and the Tarim basin in the south. The largest values are found beneath the bounding ranges. We infer that uplift of the central Tien Shan is unlikely to be caused by crustal shortening alone.