Analysis Of Source Parameters Research Articles

Application of Bayesian method for mining-induced tremors: A case study of the Xinjulong coal mine in China

Mining-induced tremor is a dynamic phenomenon occurring during the fracturing or slipping of rock and coal mass in coal mines, and the tremor mechanism is one of the key problems in the field of rockburst. The Bayesian inversion method can more accurately analyse the source rupture type under the premise of considering waveform data and model errors. First, we added different noise levels to the waveform and determined filtering parameters based on the spectrum. The rationality of the Bayesian inversion was verified by observing the focal mechanism solution. Finally, a total of fourteen mining-induced tremors were selected, and the parameters of the moment tensor (MT), type of rupture, and fault plane solutions were obtained. The results demonstrate that (1) the tremor events in the roof are mainly tensile/shear failure, and compression failure mainly occurs in the coal seam. (2) Events on the floor are closely related to gob and mining activities. (3) The rupture form of the events near the tectonic region is more complex, and the fault plane solutions (strike, dip, and slip) were obtained by MT conversion. (4) The relation between rockbursts and mining-induced tremors is discussed by analysing events 1# and 14# that occurred in the Xinjulong coal mine. These research findings can provide a reference for the analysis of source parameters and rupture forms of mining-induced tremors.

Stability Analysis of Jinchuan Hydropower Station Hydraulic Tunnels during Excavation and Unloading

As the hydropower development strategies of China continue to be implemented, a host of large hydropower projects have been completed or are being constructed in southwest China. During construction of the Jinchuan hydropower station, this study examined the stability of the surrounding rock during the excavation and unloading of hydraulic tunnels under demanding geological conditions. Microseismic (MS) monitoring technology was employed to monitor the deformation and failure of the surrounding rock online and in real time, based on engineering geological data and site surveys. To analyze the stability of the surrounding rock in the spillway tunnel and to study the temporal and spatial evolution characteristics of MS events, source parameter analysis and numerical modeling were performed. The 3D finite-difference numerical modeling software FLAC3D was used to simulate the mechanical response of the surrounding rock during the excavation and unloading of the spillway tunnel and the diversion tunnel. The numerical modeling results were compared with the monitoring results and site surveys to determine the failure mechanisms of the surrounding rock during the construction and unloading of the hydraulic tunnels. The research results can serve as a guide for studying the stability of the surrounding rock in similar hydraulic tunnels.

Multivariate Early Warning Method for Rockburst Monitoring Based on Microseismic Activity Characteristics

The monitoring of rockburst is one of the worldwide problems in underground engineering and how to effectively predict and early warn the occurrence of rockburst disasters has become an urgent problem to be solved. In this article, the high rockburst occurrence section of the deep diversion tunnel of Jinping Hydropower Station on the yalong River is taken as the research object. Based on the microseismic monitoring technology and combined with the principle of seismology with qualitative analysis and quantitative calculation, the distribution law of “time, space, and intensity” of microseismic activity and the change law of source parameters time series are used as the precursor characteristics of rockburst early warning. Based on these, the internal relationship between the microseismic activity and the rockburst micro-fracture was studied. The monitoring results show that the rockburst occurred before has obvious micro-fracture precursors. The microseismic activity is a self-organizing process from spatial disordered dispersion to ordered concentration. The abnormal changes in source parameters such as density of microseismic events, seismic energy density, the cumulative volume, energy index, 3S index, and b values can be used as a warning identification of rockburst. Therefore, the multivariate early warning method for rockburst monitoring based on the comprehensive analysis of source parameters in the deep tunnel is proposed. The prediction accuracy of this method is up to 80.6%, and it can provide reference for the rockburst prediction, warning, and safe construction of such tunnel engineering.

Empirical relationship of stochastic uncertainty of source parameters in relative local area

In the numerical simulation of strong ground motion of future destructive earthquakes, the accuracy of source parameters selection has a great impact on the results of ground motion prediction. There are many uncertain factors in determining source parameters, including both random and cognitive uncertainties. Based on a large number of seismic events and literature researches, this paper focuses on statistical analysis of source parameters with random uncertainty characteristics by using statistical methods. Through regression analysis, a mathematical model is established to explain the randomness and uncertainty of source parameters in the form of empirical formula. In order to study the scaling relation characteristics of source parameters in local regions, we get more empirical relations which are more suitable for local seismic densely regions, especially those of the local regions including the Chinese mainland. This paper more than 1 700 seismic events with MW≥5.5 are selected from the global CMT catalogue. The empirical relationship of source parameters in earthquake intensive areas is studied by using statistical methods, including focal depth, magnitude, seismic moment, rupture area, etc. The number of seismic samples of asperity in a relatively large local range is increased, so as to obtain more suitable experience for local areas to calculate source parameters from the perspective of statistics relationship. The statistical results show that there are differences between the empirical relationship of source parameters obtained from local earthquake cases and those obtained from unlimited regional cases, especially when it comes to fault rupture area and asperity related parameters. The empirical relationship of source parameters obtained from local earthquake cases is more representative. When using the empirical formula obtained in this paper to calculate the focal parameters required for the strong ground motion of future destructive earthquakes, the ground motion prediction results will better reflect the real ground motion characteristics of the target area. It could improve the reliability of the ground motion prediction results.

Automated Assessment of Glottal Dysfunction Through Unified Acoustic Voice Analysis

This paper uses the recent glottal flow model for iterative adaptive inverse filtering to analyze recordings from dysfunctional speakers, namely those with larynx-related impairment such as laryngectomy. The analytical model allows extraction of the voice source spectrum, described by a compact set of parameters. This single model is used to visualize and better understand speech production characteristics across impaired and nonimpaired voices. The analysis reveals some discriminative aspects of the source model which map to a physiological class description of those impairments. Furthermore, being based on analysis of source parameters only, it is complementary to any existing techniques of vocal-tract or phonetic analysis. The results indicate the potential for future automated speech reconstruction systems that adapt to the method of reconstruction required, as well as being useful for mainstream speech systems, such as ASR, in which front-end analysis can direct back-end models to suit characteristics of impaired speech.

Detailed Investigation of the Foreshock Sequence of the 2010 Mw7.2 El Mayor‐Cucapah Earthquake

AbstractForeshocks can provide valuable information about possible nucleation process of a mainshock. However, their physical mechanisms are still under debate. In this study, we present a comprehensive analysis of the earthquake sequence preceding the 2010 Mw7.2 El Mayor‐Cucapah mainshock, including waveform detection of missing smaller events, relative relocation, and source parameter analysis. Based on a template matching method, we find a tenfold increase in the number of earthquakes than reported in the Southern California Seismic Network catalog. The entire sequence exhibits nearly continuous episodes of foreshocks that can be loosely separated into two active clusters. Relocated foreshocks show several seismicity streaks at depth, with a consistently active cluster at depths between 14 and 16 km where the mainshock was nucleated. Stress drop measurements from a spectral ratio approach based on empirical Green's functions show a range between 3.8 and 41.7 MPa with a median of 13.0 MPa and no clear temporal variations. The relocation results, together with the source patches estimated from earthquake corner frequencies, revealed a migration front toward the mainshock hypocenter within last 8 hr and a chain of active burst immediately 6 min prior to the mainshock. Our results support combined effects of aseismic slip and cascading failure on the evolution of foreshocks.

Shape Analysis of HBT Correlations at STAR

To study the nature of the quark-hadron phase transition, it is important to investigate the space-time structure of the hadron-emitting source in heavy-ion collisions. Measurements of HBT correlations have proven to be a powerful tool to gain information about the source. In these proceedings, we report the current status of the analysis of source parameters obtained from L\'evy fits to the measured one-dimensional two-pion correlation functions in Au+Au collisions at $\sqrt{s_{NN}}$ = 200 GeV.

True Triaxial Experimental Investigation of Rock Response Around the Mine-By Tunnel Under an In Situ 3D Stress Path

Underground excavation causes rock damage, affecting its stability and fluid transport properties. Traditional experiments usually use loading regime (compressive tests) to damage the sample. However, they cannot mimic realistic in situ conditions where excavation unloading also plays a significant role. In the study, we conducted a true-triaxial acoustic emission (AE) experiment to simulate excavation-induced damage by applying in situ 3D stress path to a sample. The path originating 1.0 cm from the Mine-by tunnel crown at the Underground Research laboratory (URL) was determined using an elastic numerical model as the tunnel advanced. The computed stress path was applied to a cubic granite sample using a state-of-art true-triaxial facility to simulate rock damage in the roof. AE activity was intensively monitored, and a damaged plane was determined by fitting a plane through the localized AE events. A source parameter analysis for cluster events near the damaged plane was undertaken via a spectral fitting method. The source type was determined using the moment tensor inversion method. The source size and stress drop were also estimated. The results indicated that stress unloading plays an important role in AE activity. Temporal characteristics of AE events were converted to a spatial distribution relative to the tunnel advancement; this exhibited a good agreement with the microseismicity recorded in the tunnel roof. Source parameters (e.g., corner frequency and moment magnitude) were consistent with the field recordings. Stress drop of the experimental events ranged from 0.6 to 6 MPa, which was comparable with the higher seismicity recorded at the Mine-by tunnel roof. The stress rotation and low confinement that may cause disagreement between the laboratory and field observations are critically analyzed.

Source parameter analysis of microearthquakes recorded around the underground gas storage in the Montello-Collalto Area (Southeastern Alps, Italy)

The study of seismic source parameters is crucial for understanding the origin of seismicity and retrieving information on the energy balance and the stress involved in earthquake rupture processes. In active tectonic areas, where underground industrial activities are carried out, such parameters may help to understand whether earthquakes are induced, triggered, or natural. The Montello-Collalto area (Southeastern Alps) is located in an active tectonic environment and hosts a depleted natural reservoir used to store gas. Since 2012, a high-quality seismic network monitors the microseismicity occurring around the underground gas storage reservoir to understand if the storage activity might induce seismicity. In this paper, we estimate the source parameters of low magnitude events representative of the seismicity occurring in the area surrounding the reservoir. The analysis includes a preliminary removal of the site effects, specifically computed within this study, from all the records. Then, using a parametric multistep inversion scheme, we estimate the seismic moment, the corner frequency and the static stress drop, that can be set as reference for the microseismicity occurring in the study area. All the investigated earthquakes show low seismic efficiency compatible with overshoot processes, which is typical of natural (i.e., tectonic) earthquakes. Our procedure can be implemented in other tectonic regions hosting underground industrial activities to support the decisional processes related to real-time monitoring.

An integrated analysis of source parameters, seismogenic structure, and seismic hazards related to the 2014 MS 6.3 Kangding earthquake, China

On 22 November, 2014, an MS 6.3 earthquake occurred in Kangding County, China. Focal mechanism solution shows that the two nodal planes were 235°/82°/−173° and 144°/83°/−8° and the focal depth was 9km. Seismic slip of the Kangding earthquake was bilateral with about 0.5m maximum slip. The rupture zone was confined to depths ranging from 5 to 15km and laterally extended along the slip and strike directions by about 10 and 12km, respectively. Most of the seismic moment was released in the first 5s of the rupture, resulting in an earthquake magnitude of MW 6.01. In contrast, a slip model obtained by interferometric synthetic aperture radar (InSAR) data indicates that the rupture zone was longer than that determined from the seismic data and the earthquake magnitude should be about MW 6.2. Although accounting for the contribution of the MS 5.8 aftershock and the other small aftershocks that occurred during the InSAR observations period, the total moment estimated based on the seismic slip model was significantly smaller than that obtained from the InSAR data. Based on our analysis, we found that the inconsistency between the results determined from the seismic data and the InSAR data may be caused by the decrease in the shear modulus at shallow depths, the noise in the InSAR data, and the occurrence of some afterslips in the northwest region of the fault zone. The seismic slip of this earthquake was too small to release the accumulated energy within the entire Xianshuihe fault. We also found that the Coulomb stress in the northwest zone of the Kangding–Daofu seismic gap increased as a result of the historical, 2008 MS 8.0 Wenchuan and the 2014 MS 6.3 Kangding earthquakes, suggesting that this area is expected to be a high seismic hazard region for the future.

Detecting Significant Stress Drop Variations in Large Micro-Earthquake Datasets: A Comparison Between a Convergent Step-Over in the San Andreas Fault and the Ventura Thrust Fault System, Southern California

A key parameter in engineering seismology and earthquake physics is seismic stress drop, which describes the relative amount of high-frequency energy radiation at the source. To identify regions with potentially significant stress drop variations, we perform a comparative analysis of source parameters in the greater San Gorgonio Pass (SGP) and Ventura basin (VB) in southern California. The identification of physical stress drop variations is complicated by large data scatter as a result of attenuation, limited recording bandwidth and imprecise modeling assumptions. In light of the inherently high uncertainties in single stress drop measurements, we follow the strategy of stacking large numbers of source spectra thereby enhancing the resolution of our method. We analyze more than 6000 high-quality waveforms between 2000 and 2014, and compute seismic moments, corner frequencies and stress drops. Significant variations in stress drop estimates exist within the SGP area. Moreover, the SGP also exhibits systematically higher stress drops than VB and shows more scatter. We demonstrate that the higher scatter in SGP is not a generic artifact of our method but an expression of differences in underlying source processes. Our results suggest that higher differential stresses, which can be deduced from larger focal depth and more thrust faulting, may only be of secondary importance for stress drop variations. Instead, the general degree of stress field heterogeneity and strain localization may influence stress drops more strongly, so that more localized faulting and homogeneous stress fields favor lower stress drops. In addition, higher loading rates, for example, across the VB potentially result in stress drop reduction whereas slow loading rates on local fault segments within the SGP region result in anomalously high stress drop estimates. Our results show that crustal and fault properties systematically influence earthquake stress drops of small and large events and should be considered for seismic hazard assessment.

Identifying and Describing a Seismogenic Zone in a Sublevel Caving Mine

Analysis of caving-induced seismicity can aid in the understanding of rock mass behaviour in the different stages of the caving process. A detailed analysis of caving-induced seismicity at the Telfer sublevel caving mine was undertaken. Interpretation of seismic data in the Telfer mine showed the influence of the major geological features on cave behaviour and helped to identify the phases of cave evolution. Two geological zones with unique seismic characteristics (the M50 and M30 stiff reefs) and four key caving phases (initial undercut blasting, cave initiation, cave propagation and breakthrough) were defined through seismic data analysis. Movement of the seismogenic zone was significantly affected by the stiff reefs within the cave column. Seismic source parameter analysis was used to investigate caving mechanisms at Telfer.

A laboratory acoustic emission experiment under in situ conditions

AbstractIn this paper, we revisit acoustic emission (AE) data from an in situ rock fracture experiment conducted at the Underground Research Laboratory (URL) in Manitoba, Canada. The Mine‐By experiment, a large‐scale excavation response test, was undertaken at a depth of 420 m and involved the mechanical excavation of a cylindrical tunnel. During the experiment a small array of 16 Panametrics V103 AE sensors enclosed a 0.7 m × 0.7 m × 1.1 m rectangular prism of Lac du Bonnet granite located in the tunnel wall. The V103 sensors were later calibrated in the laboratory, and a source parameter analysis was undertaken using a spectral fitting method. Corner frequency and moment magnitude were found to be inside the ranges 250 kHz <fc< 490 kHz and −7.5 <Mw<−6.8, respectively. Static stress drops ranged from 0.3 to 4 MPa, which is consistent with large seismicity recorded at the URL.

Characteristics of Earthquake-Generated Tsunamis in Indonesia Based on Source Parameter Analysis

We have characterized 27 earthquake-generated tsunamis from 1991 to 2012 in Indonesia, based on source parameter analysis. This includes the focal mechanism derived by W phase inversion analysis, the ratio ( Θ ) between the seismic energy ( E ) and the seismic moment ( Mo ), the moment magnitude ( Mw ), the rupture duration ( To ) and the distance of the hypocenter to the trench. Most of the earthquakes (24 events) were tsunamigenic earthquakes with various fault types, a shallow focal depth (12 km ≤ D ≤ 77.8 km), a small to large magnitude (6.6 ≤ Mw ≤ 9.0), a low ratio of seismic energy to seismic moment (-5.8 < Θ < -4.9), a short to long rupture duration (27 s ≤ To ≤ 257 s), a small to large tsunami height (0.1 m ≤ H ≤ 50.9 m) and a short to long distance from the hypocenter to the trench (10 km < HT ≤ 230 km). Three tsunami earthquakes were characterized by a thrust fault mechanism, a very shallow depth ( D ≤ 20 km), a moderate magnitude (7.5 ≤ Mw ≤ 7.8), a very low ratio of seismic energy to seismic moment ( Θ ≤ -5.8), a long rupture duration (99 s ≤ To ≤ 135 s), a large tsunami height (7.4 m ≤ H ≤ 14 m) and a short distance from the hypocenter to the trench ( HT ≤ 20 km).

Feeding at a high pitch: Source parameters of narrow band, high-frequency clicks from echolocating off-shore hourglass dolphins and coastal Hector’s dolphins

Toothed whales depend on echolocation for orientation and prey localization, and source parameters of echolocation clicks from free-ranging animals therefore convey valuable information about the acoustic physiology and behavioral ecology of the recorded species. Recordings of wild hourglass (Lagenorhynchus cruciger) and Hector's dolphins (Cephalorhynchus hectori) were made in the Drake Passage (between Tierra del Fuego and the Antarctic Peninsular) and Banks Peninsular (Akaroa Harbour, New Zealand) with a four element hydrophone array. Analysis of source parameters shows that both species produce narrow band high-frequency (NBHF) echolocation clicks. Coastal Hector's dolphins produce clicks with a mean peak frequency of 129 kHz, 3 dB bandwidth of 20 kHz, 57 micros, 10 dB duration, and mean apparent source level (ASL) of 177 dB re 1 microPa(p.-p.). The oceanic hourglass dolphins produce clicks with mean peak frequency of 126 kHz, 3 dB bandwidth of 8 kHz, 116 micros, 10 dB duration, and a mean estimated ASL of 197 dB re 1 microPa(p.-p.). Thus, hourglass dolphins apparently produce clicks of higher source level, which should allow them to detect prey at more than twice the distance compared to Hector's dolphins. The observed source parameter differences within these two NBHF species may be an adaptation to a coastal cluttered environment versus a deep water, pelagic habitat.

Sensitivity Analysis of Source Parameters for Earthquake-Generated Distant Tsunamis

This paper presents a sensitivity analysis of the effects of different fault plane parameters on earthquake generated tsunamis in the far field. The parameters studied include the location of epicenter, rake angle, dip angle, strike angle, fault plane dimensions, slip displacement, and focal depth. The study was carried out by applying the verified Cornell COMCOT tsunami model to simulate distant tsunamis generated by earthquakes in three different seismic regions, namely, Japan, Aleutian Islands, and Chile in the Pacific Basin. In this study, each fault plane parameter was varied and its effect on the tsunami wave height at a distant location (Hawaii offshore waters as a case study) was examined. Our results showed that under the same earthquake magnitude, in general, variations within a reasonable range of uncertainty in rake and dip angles, epicenter location, and focal depth do not affect the resulting tsunamis significantly while a variation in the fault dimensions, strike angle, and slip displacement can cause a large change in the wave heights in the far field. The study revealed that the sensitivity of the far field wave height to certain earthquake parameters including the fault plane dimensions, slip displacement, and the strike angle does not always decrease as the distance between the earthquake and the far field increases. These results indicate the importance of accurate earthquake information for accurate tsunami predictions and that even for wave heights in a far field thousands of miles away, the earthquake may not be treated as a simple point source described by its epicenter location and magnitude alone.

Source parameters of the 2004 Kaliningrad earthquakes

An analysis of source parameters of the two unexpected earthquakes from the Kaliningrad (Russia) area is presented. The earthquakes occurred on 21 September 2004 at 11:05:01 and 13:32:31 UT, respectively. The first event was located at the latitude φ = 54.924°N and the longitude λ = 20.120°E, with a depth h = 16 km, and the second event at φ = 54.876°N, λ = 20.120°E and h = 20 km.

Coda Q c Attenuation and Source Parameter Analysis in Friuli (NE Italy) and its Vicinity

— The digital data acquired by 16 short-period seismic stations of the Friuli-Venezia-Giulia seismic network for 56 earthquakes of magnitude 2.3–4.7 which occurred in and near NE Italy have been used to estimate the coda attenuation Q c and seismic source parameters. The entire area under study has been divided into five smaller regions, following a criterion of homogeneity in the geological characteristics and the constrains imposed by the distribution of available events. Standard IASPEI routines for coda Q c determination have been used for the analysis of attenuation in the different regions showing a marked anomaly in the values measured across the NE border between Friuli and Austria for Q 0 value. A large variation exists in the coda attenuation Q c for different regions, indicating the presence of great heterogeneities in the crust and upper mantle of the region. The mean value of Q c (f) increases from 154–203 at 1.5 Hz to 1947–2907 at 48 Hz frequency band with large standard deviation estimates.¶Using the same earthquake data, the seismic-moment, M 0, source radius, r and stress-drop, Δσ for 54 earthquakes have been estimated from P- and S-wave spectra using the Brune's seismic source model. The earthquakes with higher stress-drop (greater than 1 Kbar) occur at depths ranging from 8 to 14 km.

Pitch perception physiology and psychophysics as a basis for the design of pitch detection algorithms

The generation of high‐quality speech with a source‐filter vocoder depends to a very great extent on accurate analysis of source parameters. After decades of research, even state‐of‐the‐art pitch detection algorithms tend to make gross errors in the analysis of signals that present no difficulty for the human listener. In this study a review of a broad range of pitch detection algorithms was undertaken, with particular attention to the plausibility of those algorithms in relation to what is currently known about the psychophysics of pitch perception and the neural coding of speech signals. Our principal conclusion from this review is that the most plausible model is a time‐domain pitch perception scheme proposed more than 4 decades ago by Licklider [J. C. R. Licklider, Experientia 7, 128–133 (1951)], and extended in more recent studies. The implications of these findings for source‐filter vocoders will be discussed, and an implementation of the Licklider model using level‐crossing interval histograms will be described.

The 1986 Kermadec earthquake and its relation to plate segmentation

To evaluate the tectonic significance of the October 20, 1986 Kermadec earthquake (M w =7.7), we performed a comprehensive analysis of source parameters using surface waves, body waves, and relocated aftershocks. Amplitude and phase spectra from up to 93 Rayleigh waves were inverted for centroid time, depth, and moment tensor in a two-step algorithm. In some of the inversions, the time function was parameterized to include information from the body-wave time function. The resulting source parameters were stable with respect to variations in the velocity and attenuation models assumed, the parameterization of the time function, and the set of Rayleigh waves included. The surface wave focal mechanism derived (ϕ=275°, δ=61°, λ=156°) is an oblique-compressional mechanism that is not easy to interpret in terms of subduction tectonics. A seismic moment of 4.5×1020 N-m, a centroid depth of 45±5 km, and a centroid time of 13±3 s were obtained. Directivity was not resolvable from the surface waves. The short source duration is in significant contrast to many large earthquakes.