Q0 Values Research Articles

Delineation of partial melts and crustal heterogeneities within the crust beneath Kumaon Himalaya, India from Lg wave attenuation

The crustal seismic attenuation or the Q structure is studied by using the Fourier spectra of Lg-wave along the Tanakpur- Dharchula- Dharma transect in the Kumaon Himalaya. The 1 Hz Lg Q (Q0) values are computed between different pairs of two stations and the observed values are later utilized to calculate the lateral variation in the Q0 values by following a back projection algorithm. This computation of Q0 values utilizes five regional distance earthquakes having moment magnitude (Mw) ≥ 4.0, which lie along the great circle path of the transect. Three of the five earthquakes occurred in the Tibetan plateau and the and the others occurred to the southwest on the Indian shield and are well recorded at all the 32 broadband seismographs operated between September 2018 and March 2022. The estimate Qo values range from 63 ± 2 and 203 ± 25, with the lowest value in the Lesser Himalaya and the highest across part of the Indo Gangetic Plain and Siwalik Himalaya. The Q0 model has low values ∼200 along the profile in the Indo Gangetic Plain and the Siwalik Himalaya, and are correlated with 2–5 km thick sedimentary layers below the Himalaya and the adjoining Indo-Gangetic Plain. We observe two distinctly different Q0 values to the northeast in the Lesser Himalaya tectonic unit. The region lying between the South Almora Thrust (SAT) and the Berinag Thrust (BT) shows extremely low Q0 values (∼60) but increases further north towards the Vaikrita Thrust (VT) to ∼200. The possible explanation for observing such huge variation of the Q0 values within a single tectonic unit may be the presence of fluid rich ramp structures, which introduces crustal heterogeneities and traps the aqueous fluids or partial melts lying within the crust. The Lg Q0 values decrease to the North and become ∼166 for station pairs in the Higher Himalaya and Tethys Himalaya tectonic units. The low Q0 values observed in this region may be correlated with low viscous partial melts in the form of Miocene leucogranite plutons, which resulted out of the Indo-Asian collision. The attenuation structure along the profile in the Kumaon Himalaya can be used to estimate ground motions of future earthquakes in the area and can contribute to seismic hazard assessment in the Himalaya and neighbouring regions.

Comparison of derived correction factors for effects of ion recombination and photon beam quality index following TG-51 and TRS-398 dosimetry protocols

In this study, ion recombination correction factor (kS) and beam quality conversion factor (kQ,Q0) values were extracted following the recommendations of the TRS-398 and TG-51 dosimetry protocols for widely used cylindrical ionization chambers for high energy photon beam dosimetry to quantify the agreement between the instructions for these two protocols for absolute dosimetry inside water. Four different types of cylindrical ionization chambers comprising Farmer (TM30013), Semiflex 0.125 cm3 (TM31010), Semiflex 0.3 cm3 (TM31013), and PinPoint (TM31016) were considered, and kS and kQ,Q0 values were determined at photon energies of 6 MV and 15 MV. The maximum difference between the measured kS values according to the instructions in the TRS-398 and TG-51 protocols was 0.03%. The kS data measured with both protocols agreed well with those measured by using the Jaffe-plot approach, where the maximum difference was about 0.33%. The observed differences between the kQ,Q0 factors measured by using the TRS-398 and TG-51 dosimetry protocols at photon energies of 6 MV and 15 MV were 0.37% and 0.55%, respectively. The kQ,Q0 values measured using the TG-51 dosimetry protocols were slightly closer to those measured by a reference ionization chamber dosimeter. We conclude that the maximum differences were about 0.4% and 0.6% in the absorbed dose measurements according to the TRS-398 and TG-51 instructions at photon energies of 6 MV and 15 MV, respectively. The type of ionization chamber employed also affected the differences, where the maximum and minimum dose differences were found using the Farmer and PinPoint chambers, respectively.

Hydroxypropyl methylcellulose-sugarcane bagasse adsorbents for removal of 17α-ethinylestradiol from aqueous solution and freshwater.

Adsorbents made of hydroxypropyl methylcellulose (HPMC) and sugarcane bagasse (BG) microparticles were applied for the separation of 17α-ethinylestradiol (EE2) from aqueous solution in batch, and from aqueous solution and freshwater in fixed-bed columns. HPMC chains and BG microparticles were crosslinked by the esterification with citric acid. The adsorbents presented compression modulus values that increased from 208 ± 20kPa (pure HPMC) to 917 ± 90kPa, when the content of BG particles added to HPMC was 50 wt% (HPMC50BG). The porosity (~ 97%), specific surface area (1.16 ± 0.10 m2/g) and swelling degree (20 ± 1g water/g) values were not affected by the addition of BG particles. The adsorption isotherms determined for EE2 on HPMC and on HPMC50BG fitted to the Langmuir and Freundlich models; the adsorption capacity of HPMC was slightly higher than that of composite HPMC50BG. Nevertheless, the addition of BG particles rendered outstanding mechanical reinforcement and dimensional stability to the adsorbents. The adsorption was driven by (i) hydrophobic interactions between EE2 methylene and aromatic groups and HPMC methyl groups, as evidenced by FTIR spectroscopy, and (ii) H bonds between HPMC and EE2 hydroxyl groups, as revealed by the adsorption enthalpy change (ΔHads) of - 45kJ/mol. Column adsorption experiments of EE2 from aqueous solution on HPMC and HPMC50BG indicated adsorptive capacity (q0) values of 8.06mg/g and 4.07mg/g, respectively. These values decreased considerably for the adsorption of EE2 from river water, probably due to the competition of EE2 with humic substances dissolved in natural water. The HPMC adsorbents could be recycled retaining up to 83% of the original efficiency.

Removal of benzonitrile and carbazole from model green-diesel derived from microalgae using metal-organic frameworks with protonated amines

The utilization of microalgae-derived fuel is very important for our sustainability. Here, adsorptive denitrogenation of model green-diesel (with considerable nitrogen-containing compounds, NCCs) was investigated to check the feasibility of adsorptive purification of fuel, derived from microalgae that is composed of NCCs. A highly porous MIL-101(Cr) (named M101) metal–organic framework was firstly modified to introduce protonated amino groups on both the linker and metallic sites of the MOF. The functionalized MOFs including P-M101-NH2-ED (P and ED mean ‘protonated’ and ethylenediamine, respectively), M101-NH2-ED, and M101-NH2 were applied (together with pristine M101 and a conventional activated carbon) in the adsorptive removal of N-containing compounds like benzonitrile (BENZ) and carbazole (CARB) from model green-diesel. The prepared P-M101-NH2-ED showed the most effective performances in the adsorption, compared with any other adsorbents known thus far. For instance, P-M101-NH2-ED adsorbed 15.6 and 3.6 times of BENZ and CARB, respectively, that of the activated carbon. The observed remarkable performances of P-M101-NH2-ED (Q0 values for BENZ and CARB are 500 and 455 mg/g, respectively), although with lower porosity than other M101s, for BENZ and CARB adsorption could be explained mainly with hydrogen bonding and hydrogen bonding/cation-π interactions, respectively. Moreover, P-M101-NH2-ED was recyclable in several cycles after simple ethanol washing. Therefore, P-M101-NH2-ED could be suggested as a plausible adsorbent to remove NCCs from green-diesel, based on remarkable performances and facile reusability.

Adsorption of metolachlor by a novel magnetic illite–biochar and recovery from soil

In this study, we investigated a highly efficient adsorbent that can be recycled from the soil. Walnut shells were used as raw materials to prepare original ecological biochar (OBC), illite modified biochar (IBC), FeCl3 modified biochar (magnetic biochar; MBC), and illite and FeCl3 modified biochar (IMBC), which were tested as low-cost adsorbents. The agents were used to remove metolachlor (MET) from soil. Scanning electron microscopy, Fourier transform infrared spectroscopy, X-ray diffraction, magnetic sensitivity curve analysis, and a series of adsorption experiments were conducted to study the interaction between illite and MBC, and the effect on MET adsorption. Compared with OBC, IMBC had more adsorption sites on the surface. IMBC improved the hole filling effect during the adsorption process. IMBC had more oxygen-containing functional groups and it performed better at removing organic matter through π-π interactions. According to the Langmuir model, the Q0 values for IBC, MBC, and IMBC were 91.74 mg g−1, 107.53 mg g−1, and 129.87 mg g−1, respectively, which were significantly higher than that for OBC (72.99 mg g−1). The response surface model was used to explore the optimal adsorption conditions for IMBC. After three regeneration cycles, the MET adsorption rate with IMBC was still 81.38% and the MET recovery rate was 98.12%. Therefore, IMBC was characterized as an adsorbent with high efficiency, low cost, and good recyclability. In addition, we propose a suitable agricultural system for recovering MBC on site in the field.

Lower crustal attenuation in northeastern Tibetan Plateau from ML amplitude

This study investigated the crustal attenuation structures of Sg and Lg waves of the northeastern Tibetan Plateau. We collected ML amplitude data recorded at 168 permanent stations between 1985 and 2016 and 11 temporary broadband stations between 2014 and 2016. Detailed Q0 variation maps of Sg and Lg waves were obtained by applying ML amplitude tomography. The average Q0 values of the Sg and Lg wave were 440 and 220, respectively. Relatively high attenuation anomalies of both waves appeared in the central and eastern regions of the Bayan Har Block and the east edge of the Qiangtang Block, which may be related to partial melting, high geotemperature, and strong tectonic processes. High attenuation anomalies were also found in the Qilian Orogenic Belt and Hetao Graben, which may be related to their active tectonic behavior and densely distributed faults. The relatively low attenuation anomalies of both waves were revealed in the Alax and Ordos blocks, Qaidam, Tarim, Qinghai Lake, and Gonghe basins, which can be explained by the tectonically stable properties and ancient composition of geological elements. These results indicate that the path between the highly attenuated lower crust of the Bayan Har Block and the Qilian Orogenic Belt is obstructed by three adjacent low attenuated areas (i.e., the Qilian, Qinghai Lake, and Gonghe basins); thus, it appears unlikely that a crustal flow channel from the interior of the Tibetan Plateau to the Qilian Orogenic Belt will form.

Performance column adsorption of methylene blue using composite spent coffe ground-copper ferrites (SCG/CuFe2O4)

Composite Spent Coffe Ground-Copper Ferrites (SCG/CuFe2O4) synthesized by the method of precipitation. Copper nitrate, Ferri nitrate, SCG and sodium hydroxide mixed and stirred at 80°C for 5h, then calcined at 600°C for 2 h. The purpose of this research is to determine capacity adsorption SCG/CuFe2O4 to adsorb Methylen Blue (MB) with a column system. Approximately 0.5 g of SCG/CuFe2O4 were packed in to the column. Infusion tube filled with 250 mL MB 20 mg.L-1 was adjusted to pH 10, streamed into the column with flow rate 0.8 mL/min and 1.2 mL/min. The results obtained show that the faster the flow rate, the adsorption capacity (q0) and Thomas constant (kTh) MB increase. The highest q0 and kTh values were obtained at a flow rate of 0.8 L/min at 80.13 mg/g, 0.0028 L/mg. min.Desorption of CuFe2O4 with 0.1 M HCl solution show with 3 times elution, all MB bound to the adsorbent can be removed.

A Database Retrieval Method for the Prediction of Reduced Luminance Coefficient Tables of A Road Surface Based on Measurements in Situ

ABSTRACT The in-situ measurements for r-tables have attracted special attention owing to their advantages, including increased speed, simplicity of use, and nondestructive road effects. This study presents a database retrieval method proposed for the construction of a full-scale r-table from an r-table database with 25 r coefficients used as input parameters. The proposed method was used in an in-situ, r-table measurement device as a data processing algorithm. To evaluate the accuracy of the proposed method, we performed a) a table-to-table comparison of Q0, S1, and r-tables constructed by different methods and b) comparisons of calculated luminance values (Lave, U0, Ul ) for a typical road-lighting scenario based on the use of different r-tables. The table-to-table comparison results indicate that following the application of the proposed method, its calculated Q0, S1, and r-table values were very close to their actual values (EQ0 = 2.1%, ES1 = 5.0%, Error = 2.3%). Moreover, the proposed method also exhibits an improved luminance response and achieves a 2.1% difference in Lave , a 3% difference in U0 , and a 1.8% difference in Ul . This study proves that the proposed database retrieval method improves the model prediction accuracy.

Polyaniline-derived carbons: Remarkable adsorbents to remove atrazine and diuron herbicides from water

The contamination of water resources by hazardous organic compounds is becoming severe worldwide. In this study, the adsorptive removal of atrazine (ATZ) and diuron (DUR), two widely used herbicides, from water by polyaniline-derived carbons (PDCs) was investigated for the first time, under various conditions. A selected PDC, fabricated at optimum conditions, i.e., by pyrolysis at 800 °C (and labeled PDC(800)), showed remarkable adsorptivity for both herbicides, that is, 7.7 and 11.3 times the maximum adsorption capacity (Q0) for ATZ and DUR, respectively, compared to activated carbon (AC). Or, the Q0 values of PDC(800) for ATZ and DUR were 943 and 884 mg/g, respectively; however, the Q0 values of AC were only 123 and 78.0 mg/g, respectively. Moreover, the optimum adsorbent PDC(800) had 4.5 and 3.1 times Q0 that of the best adsorbent, that showed the highest performances, so far, for ATZ and DUR, respectively. Plausible adsorption mechanisms were suggested based on the porosity and the adsorption in a wide pH range. The new adsorbent was reusable via simple solvent washing. Based on its remarkable adsorption performance and facile reusability, PDC(800) can be considered a promising adsorbent to remove herbicides such as ATZ and DUR from contaminated water.

Measurement of RF characteristics for Superconducting Quarter-wave Resonator

RF characteristics of unloaded quality factor (Q0) and accelerating electric field (Eacc) were measured for superconducting quarter-wave resonator (QWR) in order to verify the performance. For the accurate measurement of RF characteristics, the measurement method of Q0 based RF power and RF coupling coefficient was used, and the measurement uncertainty was calculated with statistics analysis of systematic error in RF measurement system. The superconducting QWR was designed with a resonant frequency of 101.28 MHz and an accelerating electric field (Eacc) of 6 MV/m at a cavity dissipation power of 10 W in the high-intensity and energy isotope separator online device (HIE-ISOLDE) project at CERN. Q-slopes and RF coupling coefficients were measured for three QWRs at the resonant frequency 101.28 MHz. Q0 values of QWRs were measured 4.55 × 108, 3.78 × 108 and 3.17 × 108 at the 6 MV/m, respectively, and the measurement uncertainty of Q0 and Eacc were calculated 2.92% and 3.32%. Performances of superconducting QWRs were acceptable to operate the beam acceleration with consideration of cryomodule capacity in HIEISOLDE project.

Добротность центральной части ВЕП, определенная по коде волны Lg по данным МСГ «Михнево»

Whereas the quality factor Q is one of the basic parameters required in seismic hazard estimation, no systematic studies of seismic attenuation factors have been carried out in the central part of the East European Platform due to the lack of a dense seismic network and a small number of regional earthquakes. The main part of the events, recorded by the small aperture array “Mikhnevo” 80 km to the south of Moscow, consists of industrial explosions of different magnitude. The idea of the paper is to apply conventional seismic methods to the analysis of seismic waveforms of industrial explosions. The paper focuses on the Lg coda of the quarry blast in “Mikhailovsky” quarry 300 km from the array. Vertical components of the short-period and broad band records of the sensors positioned in the well at the depth 20 m are processed according to the SSR algorithm, suggested by Xie and Nuttli, 1988, and extensively used by Mitchell et al in different regions of the world. The advantages of the method imply exclusion of the source and site characteristics by taking spectral ratios of the successive time windows of the coda. Compared to the earthquake waveforms, the Lg coda of explosions is shorter, less regular and contains higher frequencies. The length of coda varies according to the noise level. We selected 14 events from the same quarry in different years, which demonstrate remarkable stability of the waveforms. All the events were processed individually to obtain the frequency dependence of Q in the form Q(f)=Q0 f , where Q0 is the Q factor at the frequency 1 Hz and  is the power. To produce stable estimates of Q0 and  individual values were averaged for frequency bands: 2-6 Hz, 2-7 Hz, 3-6 Hz, 3-7 Hz for different length of coda. The preferable frequency range for Lg coda Q studies of quarry blasts is suggested as 3-6 Hz, which avoids instability of coda in 1-3 Hz interval, presumably caused by local site effect, connected with the 3 km thick sedimentary layer. The Q estimate of Q0=584±89, =0.41±0.06 proves considerable heterogeneity of the upper crust in the region. Speaking about Q factor as an indicator of the tectonic activity, the studied area can be related to a region of moderate activity.

Sawtooth induced q-profile evolution at ASDEX Upgrade

The sawtooth induced q-profile evolution was modelled at ASDEX Upgrade and validated with imaging motional Stark effect (IMSE) measurements. The equilibrium current distribution was estimated by the coupling of a Grad–Shafranov solver and the current diffusion equation. At ASDEX Upgrade an extensive diagnostic suite allows for a reliable modelling of the current density profile and its temporal evolution as long as neo-classical current diffusion can be assumed. The sawtooth-induced central q change, , was estimated from equilibrium reconstruction between the sawtooth events without using IMSE measurements. The sawtooth-induced current relaxation is modelled with two different reconnection models, a Kadomtsev full reconnection and a newly developed fully stochastic flat-current model. Both models result in about the same sawtooth-induced 0.10–0.12 but with a small difference in the absolute q0 values. The sawtooth-induced evolution of the forward modelled MSE angles agrees well with the IMSE measurements. This confirms the assumption of neo-classical current diffusion between the sawtooth events. A sensitivity study reveals two major ingredients for a reliable interpretation of MSE measurements. Firstly, the sawtooth-induced redistribution of fast ions has to be taken into account for a reliable estimation of the Shafranov shift. The fast-ion redistribution is modelled with a particle-conserving homogeneous fast-ion pressure profile in the plasma core and a subsequent recovery time of 50 ms. Secondly, a reliable estimation of the electric field is necessary for a credible interpretation of the MSE angles.

Adsorptive removal of aromatic hydrocarbons from water over metal azolate framework-6-derived carbons

Metal azolate framework-6 (MAF-6) was pyrolyzed at 1000°C to yield MOF-derived carbons (MCs). The obtained MCs were used to eliminate aromatic hydrocarbons, including polyaromatic hydrocarbons (PAHs; e.g., naphthalene (NAP), anthracene (ATC), and pyrene (PRN)) and benzene (BZ) from water via adsorption. The adsorption results over the MCs were compared with that of pristine MAF-6 and commercial activated carbon (AC). MC obtained after 24h (MC-24) exhibited a remarkable adsorption efficiency compared to that of the other MCs (obtained after different durations), MAF-6, and AC. For example, MC-24 led to adsorptions of NAP around 17 and 2.5 times those of pristine MAF-6 and AC, respectively. Or, the maximum adsorption capacities (Q0) of MAF-6, AC and MC-24 for NAP were 14, 104 and 237mg/g, respectively. Moreover, Q0 values of MC-24 for ATC and PRN were also very high of 284 and 307mg/g, respectively. Based on the properties of PAHs and the hydrophobicity of MC-24, hydrophobic interaction was suggested as the main mechanism for the adsorption of PAHs and BZ. In addition, MC-24 can be recycled by washing with acetone with little loss in performance. Therefore, MC-24 is recommended as a competitive adsorbent for aromatic hydrocarbon removal from water.

Novel approach in k0-NAA for highly concentrated REE Samples

The present paper presents a new approach for k0-NAA for accurate quantification with short turnaround analysis times for rare earth elements (REEs) in high content mineral matrices. REE k0 and Q0 values, spectral interferences and nuclear interferences were experimentally evaluated and improved with Alfa Aesar Specpure Plasma Standard 1000mgkg-1 mono-rare earth solutions. The new iterative gamma-ray self-attenuation and neutron self-shielding methods were investigated with powder standards prepared from 100mg of 99.9% Alfa Aesar mono rare earth oxide diluted with silica oxide. The overall performance of the new k0-NAA method for REEs was validated using a certified reference material (CRM) from Canadian Certified Reference Materials Project (REE-2) with REE content ranging from 7.2mgkg-1 for Yb to 9610mgkg-1 for Ce. The REE concentration was determined with uncertainty below 7% (at 95% confidence level) and proved good consistency with the CRM certified concentrations.

Regional variation of coda Q in Kopili fault zone of northeast India and its implications

Kopili fault has been experiencing higher seismic and tectonic activity during the recent years. These kind of active tectonics can be inspected by examining coda-wave attenuation and its dependence with frequency. Exploiting single back-scattering model, we have endeavored to measure coda Q and its associated parameters such as frequency dependent factor (n) and attenuation coefficient (γ) covering seven lapse-time windows spanning from 30 to 90s and central frequencies 1.5, 3.5, 6, 9 and 12Hz. The average estimated values of QC increases with frequency and lapse time window from 114 at frequency 1.5Hz to 1563 at frequency 12Hz for 30s window length, and from 305 at frequency 1.5Hz to 2135 at frequency 12Hz for 90s window length. The values of Q0 and n are also estimated for the entire Kopili fault zone. For this study region, the Q0 values vary from 62 to 348 and n varies from 0.57 to 1.51 within the frequency range 1.5 to 12Hz. Furthermore, depth variation of attenuation of this region reveals that there is velocity anomaly at depth 210–220km as there arises sharp changes in γ and n which are supported by available data, reported by other researcher for this region. Finally, we have tried to separate the intrinsic and scattering attenuation for this area. It is observed that the entire region is dominated by mainly scattering attenuation, but we can see an increase in intrinsic attenuation with depths in two stations namely TZR and BKD. Furthermore, the obtained results are comparable with the available global data.

The issues in the development of a [formula omitted] MHz, [formula omitted] superconducting half-wave resonator for the Rare Isotope Science Project (RISP)

A f=162.5 MHz superconducting half-wave resonator (HWR) with β=0.12 is one of the four superconducting cavities being developed for the heavy ion linac of the Rare Isotope Science Project (RISP). The linac will accelerate various ions ranging from proton to uranium with beam power of about 400 kW. In particular, the HWR’s will accelerate the ion beam in low–medium energy range, i.e., from 1.6 to 18 MeV for the case of uranium. In this paper, we describe design, fabrication, surface treatment, and vertical test of the 1st prototype of the cavity in detail. We also discuss some issues on the performance enhancement of the cavity. The Q0 values at 2 K surpassed the target performance, Q0=1.1×109 at Eacc=6.3MV∕m.

Determination of effective resonance energy for the 193Ir(n,γ)194Ir reaction by the cadmium ratio method

In this work, the effective resonance energy, E¯r-value for the 193Ir(n,γ)194Ir reaction was measured using cadmium ratio method. A dual monitor (197Au–98Mo), which has convenient resonance properties, was employed for characterization of the irradiation sites. Then analytical grade iridium oxide samples diluted with CaCO3 to lower neutron self-shielding effect stacked in small cylindrical Teflon boxes were irradiated once with a 1mm thick Cd cylindrical box placed in a thermalized neutron field of an 241Am–Be neutron source then without it. The activities produced in samples during 193Ir(n,γ)194Ir reaction were measured using a p-type HPGe detector γ-ray spectrometer with a 44.8% relative efficiency. The correction factors for thermal, epithermal neutron self-shielding (Gth, Gepi), true coincidence summing (Fcoi) and gamma-ray self-absorption (Fs) effects were determined with appropriate approaches and programs. Thus, the experimental E¯r-value was determined to be 2.65±0.61eV for 193Ir target nuclide. The recent data for Q0 and FCd values for E¯r determination were based on k0-NAA online database. The present experimental E¯r value was calculated and compared with more recent values for Q0 and FCd for 193Ir. Additionally, the E¯r-values was theoretically calculated from the up-to-date resonance data obtained from ENDF/B VII library using two different approaches. Since there is no experimentally determined E¯r-value for the 193Ir isotope, the results are compared with the calculated ones given in the literature.

Measurement of k 0 and Q 0 values for lutetium and europium

It was shown that the k0-method using the recently developed extended Hogdahl formalism for non-1/v nuclides and neutron temperatures from thermocouple readings can give k0-NAA results for Eu and Lu accurate to about 1 %. The necessary Q0 and k0 values for 151Eu(n,γ)152Eu, 151Eu(n,γ)152mEu and 176Lu(n,γ)177Lu were measured by reactor irradiation of certified standards and gamma-ray counting. The present measurements of k0-values did not confirm the previously published values; they were higher by 6 % for 152Eu and by 16 % for 152mEu.

Lg attenuation tomographic models of Himalaya and southern Tibet

We investigate the Lg attenuation structure of the crust beneath the tectonically complex Himalaya and southern Tibet regions adopting a tomographic regionalization method. A total of 1671 earthquake waveforms registered at 38 seismic stations operated in the region are selected for the initial LgQ measurements using the standard two-station method. Q0 (1Hz LgQ) values of 76 high quality interstation paths are finally considered as input for the tomographic inversion. The estimates of Q0 exhibit distinct variations in the crustal attenuation from north to south across the whole region. The zones of lowest Q0 values (<50) are observed along the Main Central Thrust (MCT) in Sikkim, Lesser Himalaya and some parts of the Greater Himalaya. Southern Tibet is characterized by low Q0 (<100) values. These observations are consistent with the results of body wave attenuation and velocity structure reported for the region. We interpret the variations in the attenuation characteristics in terms of both the intrinsic and scattering contributions caused by thermal effects, presence of aqueous fluids as well as heterogeneities present below these seismically active regions. Our results are found to be comparable with the other parts of Himalaya and Tibet.

Lapse time dependence of coda wave attenuation in Central West Turkey

The attenuation of coda waves has been inferred for Central West Turkey, which is characterized by a very complex tectonic evolution. The selected dataset is composed of 440 waveforms from 228 local earthquakes with a magnitude range of 2.9–4.9. The coda quality factor (Qc) was estimated for five central frequencies (fc=1.5, 3, 5, 7, 10Hz) and eight lapse times (tL, ranging from 25 to 60s), based on the assumption of single isotropic scattering model. Estimated Qc values were strongly dependent on frequency and lapse time. The frequency dependence of Qc values for each lapse time was inferred from Qc(f)=Q0fn relationships. Q0 values change between 32.7 and 82.1, while n values changes between 0.91 and 0.79 for the lapse times of 25 and 60s, respectively. The obtained low Q0 values show that the Central West Turkey region is characterized by a high seismic attenuation, in general. The whole region was divided into four subregions to examine spatial differences of attenuation characteristics. Obtained 1/Q0 and n values versus the lapse time for each subregion implies the tectonic complexity of the region. Lapse time dependencies of attenuation and n values were also examined for subdatasets from two different ranges of event depth (h<10km and h≥10km) and distance (r<40km and r≥40km). High attenuation and its high frequency dependence for long distances manifest the elevation of isotherms and increasing heterogeneity with depth. This could be associated with the extensional intra-continental plate setting, forming regional tectonics in the back-arc area.