Ionospheric <Emphasis Type="Italic">N</Emphasis><Subscript>e</Subscript> disturbances before 2007 Pu’er,Yunnan, China,earthquake

Selecting three half orbits near the epicenter of Pu’er earthquake, we analyzed the N_e data recorded in their revisited orbits during a year before this earthquake, and extracted N_e precursors. The results show that: ① There are significant seasonal variations of ionospheric N_e in night time, which exhibit different shapes respectively in four seasons; ② There are three main shapes of N_e: single-peak, saddle-shaped and even-shaped, all of which may occur in four seasons, but each season with its typical shape relatively; ③ Spatial images of N_e showed high values near the epicenter in 30 days before the earthquake, and there is a good correlation between anomaly and distribution of earthquake in space and time, which reflects that these spatial anomalies were indeed concerned with the earthquake; ④ There shows a certain similarity of the N_e curves among revisited orbits, which can provide background information for distinguishing and identification of seismic anomaly.     

Seismotectonic studies of the pleistoseist area of the <Emphasis Type="Italic">M</Emphasis> <Subscript> <Emphasis Type="Italic">s</Emphasis> </Subscript> = 6.9 Ilin-Tass earthquake in northeast Yakutia

The complex seismotectonic studies of the pleistoseist area of the Ilin-Tas earthquake (M_s = 6.9), one of the strongest seismic events ever recorded by the regional seismic network in northeastern Russia, are carried out. The structural tectonic position, morphotectonic features of present-day topography, active faults, and types of Cenozoic deformations of the epicentral zone are analyzed. The data of the instrumental observations are summarized, and the manifestations of the strong seismic events in the Yana–Indigirka segment of the Cherskii seismotectonic zone are considered. The explanation is suggested for the dynamical tectonic setting responsible for the Andrei-Tas seismic maximum. This setting is created by the influence of the Kolyma–Omolon indenter, which intrudes into the Cherskii seismotectonic zone from the region of the North American lithospheric plate and forms the main seismogenic structures of the Yana–Indigirka segment in the frontal zone (the Ilin-Tas anticlinorium). The highest seismic potential is noted in the Andrei- Tas block—the focus of the main tectonic impacts from the Kolyma–Omolon superterrane. The general trend of this block coincides with the orientation of the major axis of isoseismal ellipses (azimuth 50°–85°), which were determined from the observations of macroseismic effects on the ground after the Uyandina (M_s = 5.6), Andrei-Tas (M_s = 6.1), and Ilin-Tas (M_s = 6.9) earthquakes.     

Effect of zonal E × B plasma drift on electron density in the low-latitude ionospheric <Emphasis Type="Italic">F</Emphasis> region at a solar activity maximum near vernal equinox

The variations in the density of the ionospheric F2 layer maximum (NmF2) under the action of the zonal plasma drift perpendicularly to the magnetic (B) and electric (E) fields in the direction geomagnetic west-geomagnetic east have been studied using the three-dimensional nonstationary theoretical model of electron and ion densities (N _e and N _i ) and temperatures (T _e and T _i ) in the low-latitude and midlatitude ionospheric F region and plasmasphere. The method of numerical calculations of N _e , N _i , T _e , and T _i , including the advantages of the Lagrangian and Eulerian methods, is used in the model. A dipole approximation of the geomagnetic field (B), taking into account the non-coincidence of the geographic and geomagnetic poles and differences between the positions of the Earth’s and geomagnetic dipole centers, is accepted in the calculations. The calculated NmF2 and altitudes of the F2 layer maximum (hmF2) have been compared with these quantities measured at 16 low-latitude ionospheric sounding stations during the geomagnetically quiet period October 11–12, 1958. This comparison made it possible to correct the input model parameters: the NRLMSISE-00 model [O], the meridional component of the neutral wind velocity according to the HWW90 model, and the meridional component of the equatorial plasma drift due to the electric field specified by the empirical model. It has been indicated that the effect of the zonal E × B plasma drift on NmF2 can be neglected under daytime conditions and changes in NmF2 and hmF2 under the action of this drift are insignificant under nighttime conditions north of 25° and south of ?26° geomagnetic latitude. The effect of the zonal E × B plasma drift on NmF2 and hmF2 is most substantial in the nightside ionosphere approximately from ?20° to 20° geomagnetic latitude, and the neglect of this drift results in an up to 2.4-fold underestimation of NmF2. The found dependence of the effect of the zonal E × B plasma drift on NmF2 and hmF2 on geomagnetic latitude is related to the longitudinal asymmetry of B, asymmetry of the neutral wind about the geomagnetic equator, and changes in the meridional E × B plasma drift at a change in geomagnetic longitude.     

A first-order seismotectonic regionalization of Mexico for seismic hazard and risk estimation

The purpose of this work is to define a seismic regionalization of Mexico for seismic hazard and risk analyses. This seismic regionalization is based on seismic, geologic, and tectonic characteristics. To this end, a seismic catalog was compiled using the more reliable sources available. The catalog was made homogeneous in magnitude in order to avoid the differences in the way this parameter is reported by various agencies. Instead of using a linear regression to converts from m _b and M _d to M _s or M _w , using only events for which estimates of both magnitudes are available (i.e., paired data), we used the frequency-magnitude relations relying on the a and b values of the Gutenberg-Richter relation. The seismic regions are divided into three main categories: seismicity associated with the subduction process along the Pacific coast of Mexico, in-slab events within the down-going COC and RIV plates, and crustal seismicity associated to various geologic and tectonic regions. In total, 18 seismic regions were identified and delimited. For each, the a and b values of the Gutenberg-Richter relation were determined using a maximum likelihood estimation. The a and b parameters were repeatedly estimated as a function of time for each region, in order to confirm their reliability and stability. The recurrence times predicted by the resulting Gutenberg-Richter relations obtained are compared with the observed recurrence times of the larger events in each region of both historical and instrumental earthquakes.     

Earthquake hazard and risk assessment based on Unified Scaling Law for Earthquakes: Greater Caucasus and Crimea

We continue applying the general concept of seismic risk analysis in a number of seismic regions worldwide by constructing regional seismic hazard maps based on morphostructural analysis, pattern recognition, and the Unified Scaling Law for Earthquakes (USLE), which generalizes the Gutenberg-Richter relationship making use of naturally fractal distribution of earthquake sources of different size in a seismic region. The USLE stands for an empirical relationship log₁₀N(M, L)?=?A?+?B·(5 – M)?+?C·log₁₀L, where N(M, L) is the expected annual number of earthquakes of a certain magnitude M within a seismically prone area of linear dimension L. We use parameters A, B, and C of USLE to estimate, first, the expected maximum magnitude in a time interval at seismically prone nodes of the morphostructural scheme of the region under study, then map the corresponding expected ground shaking parameters (e.g., peak ground acceleration, PGA, or macro-seismic intensity). After a rigorous verification against the available seismic evidences in the past (usually, the observed instrumental PGA or the historically reported macro-seismic intensity), such a seismic hazard map is used to generate maps of specific earthquake risks for population, cities, and infrastructures (e.g., those based on census of population, buildings inventory). The methodology of seismic hazard and risk assessment is illustrated by application to the territory of Greater Caucasus and Crimea.     

Some Probabilistic and Statistical Properties of the Seismic Regime of Zemmouri (Algeria) Seismoactive Zone

Statistical tests have been used to adjust the Zemmouri seismic data using a distribution function. The Pareto law has been used and the probabilities of various expected earthquakes were computed. A mathematical expression giving the quantiles was established. The extreme values limiting law confirmed the accuracy of the adjustment method. Using the moment magnitude scale, a probabilistic model was made to predict the occurrences of strong earthquakes. The seismic structure has been characterized by the slope of the recurrence plot γ, fractal dimension D, concentration parameter K_sr, Hurst exponents H_r and H_t. The values of D, γ, K_sr, H_r, and H_t diminished many months before the principal seismic shock (M = 6.9) of the studied seismoactive zone has occurred. Three stages of the deformation of the geophysical medium are manifested in the variation of the coefficient G% of the clustering of minor seismic events.     

Features of Radiation and Propagation of Seismic Waves in the Northern Caucasus: Manifestations in Regional Coda

Based on the Anapa (ANN) seismic station records of ~40 earthquakes (M_W > 3.9) that occurred within ~300 km of the station since 2002 up to the present time, the source parameters and quality factor of the Earth’s crust (Q(f)) and upper mantle are estimated for the S-waves in the 1–8 Hz frequency band. The regional coda analysis techniques which allow separating the effects associated with seismic source (source effects) and with the propagation path of seismic waves (path effects) are employed. The Q-factor estimates are obtained in the form Q(f) = 90 × f 0.7 for the epicentral distances r < 120 km and in the form Q(f) = 90 × f1.0 for r > 120 km. The established Q(f) and source parameters are close to the estimates for Central Japan, which is probably due to the similar tectonic structure of the regions. The shapes of the source parameters are found to be independent of the magnitude of the earthquakes in the magnitude range 3.9–5.6; however, the radiation of the high-frequency components (f > 4–5 Hz) is enhanced with the depth of the source (down to h ~ 60 km). The estimates Q(f) of the quality factor determined from the records by the Sochi, Anapa, and Kislovodsk seismic stations allowed a more accurate determination of the seismic moments and magnitudes of the Caucasian earthquakes. The studies will be continued for obtaining the Q(f) estimates, geometrical spreading functions, and frequency-dependent amplification of seismic waves in the Earth’s crust in the other regions of the Northern Caucasus.     

Three-dimensional admittance analysis of lithospheric elastic thickness over the Louisville Ridge

Using bathymetry and altimetric gravity anomalies, a 1° 9 1° lithospheric effective elastic thickness(Te) model over the Louisville Ridge and its adjacent regions is calculated using the moving window admittance technique. For comparison, three bathymetry models are used: general bathymetric charts of the oceans, SIO V15.1,and BAT_VGG. The results show that BAT_VGG is more suitable for calculating T e than the other two models. T e along the Louisville Ridge was re-evaluated. The southeast of the ridge has a medium Te of 10–20 km, while Te increases dramatically seaward of the Tonga-Kermadec trench as a result of the collision of the Pacific and IndoAustralian plates.     

Anomalous variations in the ionospheric <Emphasis Type="Italic">F</Emphasis><Subscript>2</Subscript>-layer structure at geomagnetic midlatitudes of the Southern and Northern hemispheres at the transition from summer to winter conditions under low solar activity

The structure and dynamics of the ionosphere and plasmasphere at low solar activity under quiet geomagnetic conditions on January 15–17, 1985, and July 10–13, 1986, over Millstone Hill station and Argentine Islands ionosonde, the locations of which are approximately magnetically conjugate, have been theoretically calculated. The detected correction of the model input parameters makes it possible to coordinate the measured and calculated anomalous variations in the electron density NmF2 at the height hmF2 of the ionospheric F2 layer over Argentine Islands ionosonde as well as the calculated and measured values of NmF2 and electron temperature at the hmF2 height over Millstone Hill station. It has been shown that vibrationally excited N₂ and O₂ molecules almost do not influence the formation of the winter anomaly under the conditions of low solar activity. A difference between the influence of electronically excited O⁺ on N _e ions under winter and summer conditions forms not more than 11% of the N _e winter anomaly event in the F ₂ layer and topside ionosphere. The model without electronically excited O⁺ ions reduces the duration of the N _e winter anomaly event. It has been shown that the seasonal variations in the composition of the neutral atmosphere form mainly the NmF2 winter anomaly event over the Millstone Hill radar at low solar activity.     

Frictional and viscous effects on the nucleation phase of an earthquake

We study the frictional and viscous effects on earthquake nucleation, especially for the nucleation phase, based on a one-degree-of-freedom spring-slider model with friction and viscosity. The frictional and viscous effects are specified by the characteristic displacement, U _c, and viscosity coefficient, η, respectively. Simulation results show that friction and viscosity can both lengthen the natural period of the system and viscosity increases the duration time of motion of the slider. Higher viscosity causes a smaller amplitude of lower velocity motion than lower viscosity. A change of either U _c (under large η) or η (under large U _c) from a large value (U _ch for U _c and η _h for η) to a small one (U _cl for U _c and η _l for η) in two stages during sliding can result in a clear nucleation phase prior to the P-wave. The differences δU _c = U _ch ? U _cl and δη = η _h ? η _l are two important factors in producing a nucleation phase. The difference between the nucleation phase and the P-wave increases with either δU _c or δη. Like seismic observations, the peak amplitude of P-wave, which is associated with the earthquake magnitude, is independent upon the duration time of nucleation phase. A mechanism specified with a change of either η or U _c from a larger value to a smaller one due to temporal variations in pore fluid pressure and temperature in the fault zone based on radiation efficiency is proposed to explain the simulation results and observations.     

Shear wave velocity-based evaluation and design of stone column improved ground for liquefaction mitigation

The evaluation and design of stone column improvement ground for liquefaction mitigation is a challenging issue for the state of practice. In this paper, a shear wave velocity-based approach is proposed based on the well-defined correlations of liquefaction resistance (CRR)-shear wave velocity (V _s)-void ratio (e) of sandy soils, and the values of parameters in this approach are recommended for preliminary design purpose when site specific values are not available. The detailed procedures of pre- and post-improvement liquefaction evaluations and stone column design are given. According to this approach, the required level of ground improvement will be met once the target V _s of soil is raised high enough (i.e., no less than the critical velocity) to resist the given earthquake loading according to the CRR-V _s relationship, and then this requirement is transferred to the control of target void ratio (i.e., the critical e) according to the V _s-e relationship. As this approach relies on the densification of the surrounding soil instead of the whole improved ground and is conservative by nature, specific considerations of the densification mechanism and effect are given, and the effects of drainage and reinforcement of stone columns are also discussed. A case study of a thermal power plant in Indonesia is introduced, where the effectiveness of stone column improved ground was evaluated by the proposed V _s-based method and compared with the SPT-based evaluation. This improved ground performed well and experienced no liquefaction during subsequent strong earthquakes.     

Detailed Study of Time Variations in the Gutenberg–Richter <Emphasis Type="Italic">b</Emphasis>-value Based on Highly Accurate Seismic Observations at the Garm Prognostic Site,Tajikistan

The time variations in the Gutenberg–Richter b-value are minutely studied based on the data of highly accurate seismological observations at the Garm prognostic site, Tajikistan, where a stationary network of seismic stations of the Complex Seismological Expedition (CSE) of Schmidt Institute of Physics of the Earth (IPE) of the USSR (Russian) Academy of Sciences was in operation from 1955 to 1992. A total of 93035 local earthquakes ranging from 0.0 to 6.3 in the Ml magnitudes are considered. The spatiotemporal fluctuations in the minimal magnitude of completeness of the earthquakes, Mc, are analyzed. The study considers a 25-year interval of the observations at the center of the observation system within which Mc = 0.9. It is shown that in most cases, the b-value and log₁₀E^2/3 experience characteristic time variations before the earthquakes with magnitudes higher than the minimal magnitude of the predicted earthquake (MPE). The 6-year anomaly in the parameters’ b-value, log₁₀E^2/3, and log₁₀N associated with the single strongest earthquake with M = 6.3 that occurred in the observation region on October 26, 1984 is revealed. The inversely proportional relationship is established between the time variations in the b-value and the time variations in the velocities of seismic waves Vp and Vp/Vs. It is shown that the exponent p in the power function which links the time variations of the b-value and log₁₀E^2/3 is higher in the zones of crustal compression than in the zones of extension. It is simultaneously confirmed that the average b-value in the zones of compression is lower than in the zones of extension. It is established that in the case of earthquakes with M ≥ 2.6, the time series of seismic activity log₁₀N_i and the time series of the b-value are highly cross correlated with a coefficient of r ≈ 0.75, whereas in the case of earthquakes with M ≥ 0.9, the coefficient of cross correlation between these time series is close to zero (r ≈ 0.06). The law of variations in the slope of the lines approximating the relationship between the log₁₀N_i time series in the different magnitude ranges (M ≥ Mc_i) and b-value time series is obtained. It is hypothesized that the seismic activity of the earthquakes with high magnitudes can be estimated provided that the parameters of the time series of the b-value and time series of the number of earthquakes logN(ΔM_i) in the range of low magnitudes are known. It is concluded that using the parameter log₁₀N for prognostic estimates of the strong earthquakes only makes sense for earthquakes having moderate and large magnitudes. It is inferred that the time variations in the b-value are predominantly contributed by the time variations of the earthquakes with relatively large magnitudes.     

Soil failure can be used for seismic protection of structures

A new seismic design philosophy is illuminated, taking advantage of soil “failure” to protect the superstructure. Instead of over-designing the foundation to ensure that the loading stemming from the structural inertia can be “safely” transmitted onto the soil (as with conventional capacity design), and then reinforce the superstructure to avoid collapse, why not do exactly the opposite by intentionally under-designing the foundation to act as a “safety valve” ? The need for this “reversal” stems from the uncertainty in predicting the actual earthquake motion, and the necessity of developing new more rational and economically efficient earthquake protection solutions. A simple but realistic bridge structure is used as an example to illustrate the effectiveness of the new approach. Two alternatives are compared : one complying with conventional capacity design, with over-designed foundation so that plastic “hinging” develops in the superstructure; the other following the new design philosophy, with under-designed foundation, “inviting” the plastic “hinge” into the soil. Static “pushover” analyses reveal that the ductility capacity of the new design concept is an order of magnitude larger than of the conventional design: the advantage of “utilising” progressive soil failure. The seismic performance of the two alternatives is investigated through nonlinear dynamic time history analyses, using an ensemble of 29 real accelerograms. It is shown that the performance of both alternatives is totally acceptable for moderate intensity earthquakes, not exceeding the design limits. For large intensity earthquakes, exceeding the design limits, the performance of the new design scheme is proven advantageous, not only avoiding collapse but hardly suffering any inelastic structural deformation. It may however experience increased residual settlement and rotation: a price to pay that must be properly assessed in design.     

Force reduction factors for steel buildings with welded and post-tensioned connections

The seismic responses of steel buildings with perimeter moment resisting frames (MRF) with welded connections (WC) are estimated and compared to those of similar buildings with semi-rigid post-tensioned connections (PC). The responses are estimated in terms of ductility reduction factors (R _µ,), ductility demands (µ _G ) and force reduction factors (R). Two steel model buildings, which were modeled as complex-3D-MDOF systems, were used in the study. Results indicate that the reduction magnitude of global response parameters is larger than that of local response parameters, contradicting the same reduction implicitly assumed in the static equivalent lateral force procedure, implying that non-conservative design may result. The value of 8 for R, suggested in many codes for ductile steel MRF, and the value of 1 suggested in the well known Newmark and Hall procedure for the ratio of R to µ _G , cannot be justified. The reason for this is that SDOF systems were used to model actual structures, where higher mode effects, energy dissipation and structural overstrength weren’t explicitly considered. The codes should be more transparent regarding the magnitude and the components involved in the force reduction factors. The seismic performance of steel buildings with PC may be superior to that of the buildings with WC, since their force reduction factors are larger and their ductility demands smaller, implying that PC buildings could be designed for smaller lateral seismic forces. The conclusions of this paper are for the particular structural systems and models considered. Much more research is needed to reach more general conclusions.     

DHI evaluation by combining rock physics simulation and statistical techniques for fluid identification of Cambrian-to-Cretaceous clastic reservoirs in Pakistan

The use of seismic direct hydrocarbon indicators is very common in exploration and reservoir development to minimise exploration risk and to optimise the location of production wells. DHIs can be enhanced using AVO methods to calculate seismic attributes that approximate relative elastic properties. In this study, we analyse the sensitivity to pore fluid changes of a range of elastic properties by combining rock physics studies and statistical techniques and determine which provide the best basis for DHIs. Gassmann fluid substitution is applied to the well log data and various elastic properties are evaluated by measuring the degree of separation that they achieve between gas sands and wet sands. The method has been applied successfully to well log data from proven reservoirs in three different siliciclastic environments of Cambrian, Jurassic, and Cretaceous ages. We have quantified the sensitivity of various elastic properties such as acoustic and extended elastic (EEI) impedances, elastic moduli (K _sat and K _sat–μ), lambda–mu–rho method (λρ and μρ), P-to-S-wave velocity ratio (V _P/V _S), and Poisson’s ratio (σ) at fully gas/water saturation scenarios. The results are strongly dependent on the local geological settings and our modeling demonstrates that for Cambrian and Cretaceous reservoirs, K _sat–μ, EEI, V _P/V _S, and σ are more sensitive to pore fluids (gas/water). For the Jurassic reservoir, the sensitivity of all elastic and seismic properties to pore fluid reduces due to high overburden pressure and the resultant low porosity. Fluid indicators are evaluated using two metrics: a fluid indicator coefficient based on a Gaussian model and an overlap coefficient which makes no assumptions about a distribution model. This study will provide a potential way to identify gas sand zones in future exploration.     

Study on seismic performance enhancement in bridges based on factorial analysis

The seismic performance of bridges depends on the ductile behavior of its column, as the deck and other substructural components except pile foundations are normally designed to be elastic to facilitate bridge retrofitting.Codes such as AASHTO, Caltrans, IRC: 112 etc.give guidelines for the seismic performance enhancement of columns through ductile detailing.In the present study, a methodology for the seismic performance enhancement of bridges is discussed by using a "Parameter-Based Influence Factor"(PIF) developed from factorial analysis.The parameters considered in the factorial analysis are: percentage of longitudinal reinforcement(P_t), compressive strength of concrete(f'_c), yield strength of steel(f_y), spacing of lateral ties(S) and column height(H).The influence of each parameter and their combination on the limit states considered is estimated.Pushover analysis is used to evaluate the capacity of columns, considering shear failure criteria.A total of 243(3~5 combinations) analysis results are compiled to develop ‘PIF’ used in the performance enhancement process.The study also encompasses other sub-objectives such as evaluating the discrepancies in using the Importance Factor(I) in designing bridges of varied functional importance; and estimating the aspect ratio and slenderness ratio values of bridge columns for its initial sizing.     

Seasonal variation of carbon exchange of typical forest ecosystems along the eastern forest transect in China

The long-term and continuous carbon fluxes of Changbaishan temperate mixed forest (CBS), Qianyanzhou subtropical evergreen coniferous forest (QYZ), Dinghushan subtropical evergreen mixed forest (DHS) and Xishuangbana tropical rainforest (XSBN) have been measured with eddy covariance techniques. In 2003, different responses of carbon exchange to the environment appeared across the four ecosystems. At CBS, the carbon exchange was mainly determined by radiation and temperature. 0°C and 10°C were two important temperature thresholds; the former determined the length of the growing season and the latter affected the magnitude of carbon exchange. The maximum net ecosystem exchange (N _EE) of CBS occurred in early summer because maximum ecosystem photosynthesis (G _PP) occurred earlier than maximum ecosystem respiration (R _e). During summer, QYZ experienced severe drought and N _EE decreased significantly mainly as a result of the depression of G _PP. At DHS and XSBN, N _EE was higher in the drought season than the wet season, especially the conversion between carbon sink and source occurring during the transition season at XSBN. During the wet season, increased fog and humid weather resulted from the plentiful rainfall, the ecosystem G _PP was dispressed. The Q ₁₀ and annual respiration of XSBN were the highest among the four ecosystems, while the average daily respiration of CBS during the growing season was the highest. Annual N _EE of CBS, QYZ, DHS and XSBN were 181.5, 360.9, 536.2 and ?320.0 g·C·m^?2·a^?1, respectively. From CBS to DHS, the temperature and precipitation increased with the decrease in latitude. The ratio of N _EE/R _e increased with latitude, while R _e/G _PP, ecosystem light use efficiency (L _UE), precipitation use efficiency and average daily G _PP decreased gradually. However, XSBN usually escaped such latitude trend probably because of the influence of the south-west monsoon climate which does not affect the other ecosystems. Long-term measurement and more research were necessary to understand the adaptation of forest ecosystems to climate change and to evaluate the ecosystem carbon balance due to the complexity of structure and function of forest ecosystems.     

Attenuation coefficients of Rayleigh and <Emphasis Type="Italic">Lg</Emphasis> waves

Analysis of the frequency dependence of the attenuation coefficient leads to significant changes in interpretation of seismic attenuation data. Here, several published surface-wave attenuation studies are revisited from a uniform viewpoint of the temporal attenuation coefficient, denoted by χ. Theoretically, χ( f) is expected to be linear in frequency, with a generally non-zero intercept γ?=?χ(0) related to the variations of geometrical spreading, and slope dχ/df = π/Q _e caused by the effective attenuation of the medium. This phenomenological model allows a simple classification of χ( f) dependences as combinations of linear segments within several frequency bands. Such linear patterns are indeed observed for Rayleigh waves at 500–100-s and 100–10-s periods, and also for Lg from ~2 s to ~1.5 Hz. The Lg χ( f) branch overlaps with similar linear branches of body, Pn, and coda waves, which were described earlier and extend to ~100 Hz. For surface waves shorter than ~100 s, γ values recorded in areas of stable and active tectonics are separated by the levels of \(\gamma _{D} \approx 0.2 \times 10^{-3}\) s^???1 (for Rayleigh waves) and 8 ×10^???3 s^???1 (for Lg). The recently recognized discrepancy between the values of Q measured from long-period surface waves and normal-mode oscillations could also be explained by a slight positive bias in the geometrical spreading of surface waves. Similarly to the apparent χ, the corresponding linear variation with frequency is inferred for the intrinsic attenuation coefficient, χ _i , which combines the effects of geometrical spreading and dissipation within the medium. Frequency-dependent rheological or scattering Q is not required for explaining any of the attenuation observations considered in this study. The often-interpreted increase of Q with frequency may be apparent and caused by using the Q-based model of attenuation and following preferred Q( f) dependences while ignoring the true χ( f) trends within the individual frequency bands.     

Modeling of the thermal structure of continental lithosphere

The thermal structure of continental lithosphere (the temperature, heat flows, and heat generation in the crust and lithosphere) is reconstructed from geothermal, seismic, and petrologic data. The first step is the determination of the temperature profile from absolute P and S wave velocities (T _{P, S} ). The T _{P, S} profile is then adjusted to a thermophysical model of conductive transfer. In addition, the surface heat flow and the T _{P, S} profile are used to determine heat generation, thicknesses of crustal layers, and heat flow components in the crust and lithosphere. A feature inherent in the solution of the thermophysical inverse problem obtained in this paper is the use of constraints derived from the temperature reconstruction by seismic data inversion. As a result, the analytical dependence of the temperature on depth, the intensity of radiogenic heat sources in the crust, and heat flow components in the crust and lithosphere are determined.     

A way of estimating the characteristic slip displacement

During the ruptures of an earthquake,the strain energy.△E,.will be transferred into,at least,three parts,i.e..the seismic radiation energy(E_s),fracture energy(E_g),and frictional energy(E_f),that is,△E = E_s + E_g + E_f.Friction,which is represented by a velocity- and state-dependent friction law by some researchers,controls the three parts.One of the main parameters of the law is the characteristic slip displacement.D_c.It is significant and necessary to evaluate the reliable value of D_c from observed and inverted seismic data.Since D_c controls the radiation efficiency.η_R = E_s/(E_s+ E_g),the value of η_r is a good constraint of estimating D_c.Integrating observed data and inverted results of source parameters from recorded seismograms.the values of E_s and E_g of an earthquake can be measured,thus leading to the value of η_R.The constraint used to estimate the reliable value of D_c will be described in this work.An example of estimates of D_c.based on the observed and inverted values of source parameters of the September 20,1999 M_S 7.6 Chi-Chi(Ji-Ji).Taiwan region,earthquake will be presented.