Simulated Annealing Inversion Research Articles

The Marmara Sea basin as a regional depression constrained from ambient noise correlation tomography

SUMMARY We computed a 3-D shear wave velocity model of the Marmara Sea region from ambient noise tomography. The correlations of up to 8 yr of vertical-component seismic recordings from 80 broad-band stations provided Rayleigh wave group velocity measurements in the period band 6–21 s at more than 1400 selected virtual source–receiver pairs. Rayleigh wave group velocity maps were used to derive a shear wave velocity model through simulated annealing inversion. The resulting crustal model provides coverage of the Marmara Sea along with its surrounding regional tectonic features. This allows for an investigation of the spatial extents of the Marmara Sea on a scale larger than that of basins. The low-velocity structures of the Marmara Sea and the Thrace Basins are coeval to a depth of approximately 9 km. The crustal velocities beneath the Marmara Sea basins exhibit a low vertical gradient and smooth horizontal variations. The regional tectonic structures, such as Istranca Massif, Istanbul and Sakarya Zones, display sharp velocity contrasts with the lower velocity crust beneath the Marmara Sea. The observed low crustal velocities, along with depth variations of the velocity isosurfaces (i.e. 3.4 km s−1) indicate that the Marmara region is a structural depression much deeper and larger than the three basins of the North Marmara Trough. The North Anatolian Fault Zone is unlikely to be the primary factor contributing to the origin of this significant depression, as the basin's development appears to have occurred before the fault propagated into the region.

Improved adaptive regularization for simulated annealing inversion of transient electromagnetic

Geophysical inversion usually involves ill-posed problem. Regularization is the most commonly used method to mitigate this problem. There are many regularization parameter selection methods, among which the adaptive regularization method can automatically update parameters during iteration, reducing the difficulty of parameter selection. Therefore, it is widely used in linear inversion. However, there are very few studies on the use of adaptive regularization methods in stochastic optimization algorithms. The biggest difficulty is that in stochastic optimization algorithms, the search direction of any iteration is completely random. Data fitting term and stabilizing term vary in a wide range, making it difficult for traditional methods to work. In this paper, we consider the contributions of the data fitting term and the stabilizing term in the objective function and give an improved adaptive regularization method for very fast simulated annealing (VFSA) inversion for transient electromagnetic (TEM) data. The optimized method adjusts the two terms dynamically to make them in balance. We have designed several numerical experiments, and the experimental results demonstrate that the method in this paper not only accelerates the convergence, but also the inversion results are very little affected by the initial regularization parameter. Finally, we apply this method to field data, and the inversion results show very good agreements with nearby borehole data.

Accurate Redetermination of the Focal Depth by Using the Time Intervals between the Inner Core Phases PKIKP and pPKIKP

The hypocenter parameters of an earthquake may give us an insight into the Earth’s structure and tectonic processes. Among the hypocenter parameters, the focal depth is normally more difficult to estimate than the earthquake location (latitude and longitude). We propose to use the pPKIKP-PKIKP arrival time intervals for estimating the focal depth. We analyze the sensitivity of the pPKIKP-PKIKP arrival time interval to the earthquake depth. We measure the pPKIKP-PKIKP arrival time interval on seismograms (the vertical component), and invert the time interval data set using the simulated annealing inversion algorithm. We illustrate the inversion approach on two teleseismic earthquakes which have shallow and deep focal depths, and demonstrate that the approach is indeed appropriate to the shallow and deep event. We can obtain a reliable estimate on focal depth, even though the seismic station is sparse or in a remote part of the epicenter.

Asynchronous MMC PSA inversion of transient electromagnetic data

This paper focuses on low computational efficiency in simulated annealing (SA) inversion of Transient Electromagnetic (TEM) data. Asynchronous multiple Markov chains (MMC) parallel strategy is a very promising SA acceleration method, which can be accelerated almost linearly. However, this method also reduces the accuracy of the solution. To overcome this problem, we added the solution set strategy to the asynchronous MMC parallel simulated annealing (PSA) algorithm for the first time. In this new algorithm, each thread independently searches for direction and exchanges data with the solution set in the shared memory. We used both the synthetic and field data to test the new algorithm. The synthetic data tests showed that the MMC PSA results are better than those of the original MMC PSA. We analyzed the efficiency of the new algorithm. Compared with the sequential VFSA, the maximum speedup of the new algorithm is approximately 10 times. The field data test also showed that the improved MMC PSA algorithm has good practicability. These tests demonstrate that the improved algorithm is effective, showing that its convergence speed is greatly improved without reducing the accuracy.

Electrical Conductivity Evidence for the Existence of a Mantle Plume Beneath Tarim Basin

This paper proposes using a simulated annealing (SA) calculation to perform one-dimensional inversion of Geomagnetic Depth Sounding (GDS) to obtain the conductivity information of the lower mantle beneath the Tarim area, to calculate the temperature of the lower mantle according to the relevant formula of the petrophysical experiment, and to provide evidence of the existence of the Tarim mantle plume. The data used for inversion originate from the China Geomagnetic Network Center. This article uses theoretical data to prove that the simulated annealing algorithm can invert the true conductivity model when the data do not contain noise. However, when the data contain noise, it is more accurate to use the statistical expected value of the high-quality conductivity model during the simulated annealing inversion process as the optimal conductivity model rather than the classic simulated annealing algorithm. The simulated annealing inversion results of only four stations in Tarim area show that the conductivity of the top of the lower mantle and the upper part of the mantle transition zone in Tarim area is higher than the global average, and it is speculated that the temperature is 150k–450k higher than the global average. This is important evidence for the existence of the mantle plume beneath the Tarim Basin.

Application of fine structure interpretation and reservoir prediction technology in Beier Sag

After years of exploration in Beier Sag, the exploration is becoming more and more difficult. Beier Sag is characterized by many faults and complex structures. For a long time, the exploration and development effect of many fault blocks is not good due to unclear structure and poor reservoir prediction effect. Therefore, through the close combination of Geology and earthquake, we need to use the fine structure interpretation technology to interpret the seismic data carefully, and on this basis, we need to carry out the fine characterization of favorable reservoirs through the appropriate reservoir prediction technology. The fusion frequency inversion technology is based on improving the resolution through different inversion methods, combining with dominant frequency fusion, applying simulated annealing inversion and geostatistics (SMI) inversion to calculate separately, then fusing the inversion results of dominant frequency, and interpreting the fusion results, and finally accurately predicting the reservoir distribution in the fan body, favorable exploration targets should be implemented.

Location of Sinabung volcano magma chamber on 2013 using simulated annealing inversion scheme

Volcano has been monitoring using GPS after his eruption on August 2010. We Applied Simulated Annealing Inversion Scheme to GPS data on 2013, first we applied Simulated Annealing to velocity data on 23 January 2013 then we applied Simulated Annealing Inversion Scheme to data on 31 December 2013. From our analysis we got the depth of the pressure source modeling results indicate some possibilities that Sinabung has a deep magma chamber about 14km and also shallow magma chamber about 1km from the surface.

A Comparative Performance of Least-Square Method and Very Fast Simulated Annealing Global Optimization Method for Interpretation of Self-Potential Anomaly over 2-D Inclined Sheet Type Structure

Abstract: Inversion of self-potential anomaly for 2-D inclined sheets of infinite horizontal extent has been studied. Least-square inversion and very fast simulated annealing global optimization has been used to model the five parameters of self potential anomaly. The method of least square and very fast simulated annealing global optimization method is compared and analyzed. Very fast simulated annealing can model the noisy and field data of self potential anomaly very precisely than linear inversion technique. However, time taken by very fast simulated annealing inversion is larger than linearized inversion. The comparative analysis has been done on synthetic data (noise free and noisy) and two field data from Bavarian woods anomaly, Germany and Surda anomaly, India to show the efficacy of both the methods. The estimated parameters were compared with those from previous studies using various global optimization algorithms, mainly neural network, genetic algorithm and particle swarm optimization on the same field data sets. It can be concluded that the global optimization algorithms considered in this study were able to yield compatible solutions with those from least-square methods. The present global optimization method is in good agreement with the other global optimization methods in terms of results and computation time.

Stochastic seismic inversion using greedy annealed importance sampling

A global optimization method called very fast simulated annealing (VFSA) inversion has been applied to seismic inversion. Here we address some of the limitations of VFSA by developing a new stochastic inference method, named greedy annealed importance sampling (GAIS). GAIS combines VFSA and greedy importance sampling (GIS), which uses a greedy search in the important regions located by VFSA, in order to attain fast convergence and provide unbiased estimation. We demonstrate the performance of GAIS with application to seismic inversion of field post- and pre-stack datasets. The results indicate that GAIS can improve lateral continuity of the inverted impedance profiles and provide better estimation of uncertainties than using VFSA alone. Thus this new hybrid method combining global and local optimization methods can be applied in seismic reservoir characterization and reservoir monitoring for accurate estimation of reservoir models and their uncertainties.

Testing and verification of a scale-model acoustic propagation system.

This paper discusses the design and operation of a measurement apparatus used to conduct scale-model underwater acoustic propagation experiments, presents experimental results for an idealized waveguide, and compares the measured results to data generated by two-dimensional (2D) and three-dimensional (3D) numerical models. The main objective of this paper is to demonstrate the capability of the apparatus for a simple waveguide that primarily exhibits 2D acoustic propagation. The apparatus contains a computer-controlled positioning system that accurately moves a receiving transducer in the water layer above a scale-model bathymetry while a stationary source transducer emits broadband pulsed waveforms. Experimental results are shown for a 2.133 m × 1.219 m bathymetric part possessing a flat-bottom bathymetry with a translationally invariant wedge of 10° slope along one edge. Beamformed results from a synthetic horizontal line array indicate the presence of strong in-plane arrivals along with weaker diffracted and horizontally refracted arrivals. A simulated annealing inversion method is applied to infer values for five waveguide parameters with the largest measurement uncertainty. The inferred values are then used in a 2D method of images model and a 3D adiabatic normal-mode model to simulate the measured acoustic data.

Equivalent MFL model of pipelines for 3-D defect reconstruction using simulated annealing inversion procedure

In this paper, we propose an equivalent forward model of magnetic flux leakage (MFL) inspection in pipelines to reduce the computation effort to predict MFL signals. Then an iterative simulated annealing inversion procedure is developed to reconstruct the three-dimensional (3-D) defect profile from MFL signals. Experiments results, based on both simulated and measured MFL signals, demonstrate that the proposed inversion procedure using the equivalent forward model has high performance in terms of execution speed and accuracy.

The oil production performance analysis using discrete fracture network model with simulated annealing inverse method

Naturally fractured reservoirs generally show high production in early stage, however, the oil might decrease suddenly within a few months. Because the connectivity of fracture network directly affects the oil production, the characterization of its network is extremely important, especially in fracture basement reservoirs. In order to characterize the fracture network, we have developed integrated system of fracture generation and discrete fracture network flow model coupling with simulated annealing inversion method. With the utilization of the model, parameters (fracture density, Fisher’s constant) of fracture network were analyzed. As a result, even though the same values of parameters were applied, different network systems were observed. Therefore, further study is essential to obtain unique fracture network system.

Global nonlinear optimization for the estimation of static shift and interpretation of 1-D magnetotelluric sounding data

In the presence of conducting inhomogeneities in near-surface structures, apparent resistivity data in magnetotelluric sounding can be severely distorted. This is due to electric fields generated from boundary charges on surficial inhomogeneities. Such distortion persists throughout the entire recording range and is known as static shift in magnetotellurics. Frequency-independent static shifts manifest as vertical, parallel shifts that occur in plots of the dual logarithmic scale of apparent resistivity versus time period. The phase of magnetotelluric sounding data remains unaffected by the static shift and can be used to remove the static shift to some extent. However, individual inversion of phase data yields highly nonunique results, and alone it will not work to correctly remove the static shift. Inversions of uncorrected magnetotelluric data yield erroneous and unreliable estimations, while static-shift-corrected magnetotelluric data provide better and reliable estimations of the resistivities and thicknesses of subsurface structures. In the present study, static shift (a frequency-independent real constant) is also considered as one of the model parameters and is optimized together with other model parameters (resistivity and thickness) using the very fast simulated annealing global inversion technique. This implies that model parameters are determined simultaneously with the estimate of the static shift in the data. Synthetic and noisy data generated for a number of models are interpreted, to demonstrate the efficacy of the approach to yield reliable estimates of subsurface structures when the apparent resistivity data are affected by static shift. Individual inversions of static-shift-affected apparent resistivity data and phase data yield unreliable estimations of the model parameters. Furthermore, the estimated model parameters after individual data inversions do not show any systematic correlations with the amount of static shift in the data. The present study shows that only joint inversion of the apparent resistivity and phase data, without or with optimizing of the static shift, yields models that show good fits between the observed and the model data. Joint inversion results also reveal a systematic relationship between the estimated model parameters and the static shift in the data. The proposed approach also shows that estimated resistivities are ‘S’ (the static shift parameter) times the actual resistivities, and that estimated thicknesses are √S times the actual thicknesses without optimization of the static shift. This result is in good agreement with the existing relationship in the literature. Therefore, the global optimization procedure developed can be effectively used to optimize the static shifts in data, to obtain reliable estimations of model parameters. Subsequently, joint inversion of the apparent resistivity and phase data, with optimization of the static shift, is performed, which yields accurate estimates of subsurface structures. It is demonstrated that this approach can also be used when the data is not affected by the static shift. In such cases, the estimated static shift parameter ‘S’ will be close to unity. The efficacy of the approach is demonstrated with a field example from Singhbhum craton, eastern India, by providing an accurate estimation of the craton thickness and the conducting structure that lies below the craton. Normal 0 false false false EN-US X-NONE X-NONE

Moment-Tensor Determination by Nonlinear Inversion of Amplitudes

We propose an inversion method of the direct wave amplitudes P, SV, and SH to determine the general moment tensor (MT) and estimate the associated uncertainties. This method is a generalization of the one we developed to determine the double-couple (DC) or fault-plane solution from sparse observations in reservoir contexts (Godano et al., 2009). Like the previous one, it is based on a simulated annealing inversion algorithm. First, we test the reliability of this new method on synthetic data. The inversion allows retrieval of the expected moment tensor, but the analysis of the uncertainty associated with the solution shows that the resolution of the inversion is sensitive not only to the direct wave amplitudes but also to uncertainties in the velocity model and the event location. Next, we test the method on four induced microearthquakes recorded by the Soultz-sous-Forets hot-dry-rock (HDR) reservoir network. The inversion correctly converges for three events, and the obtained MTs display a dominant DC part (70 to 90%). The uncertainty associated with the non-DC part is relatively high. This prevents us from determining if the small non-DC part is significant or an artifact related to noise in the data and/or uncertainties in the velocity model and at the event location.

Dose Escalation to the Dominant Intraprostatic Lesion Defined by Sextant Biopsy in a Permanent Prostate I-125 Implant: A Prospective Comparative Toxicity Analysis

Using real-time intraoperative inverse-planned permanent seed prostate implant (RTIOP/PSI), multiple core biopsy maps, and three-dimensional ultrasound guidance, we planned a boost volume (BV) within the prostate to which hyperdosage was delivered selectively. The aim of this study was to investigate the potential negative effects of such a procedure. Patients treated with RTIOP/PSI for localized prostate cancer with topographic biopsy results received an intraprostatic boost (boost group [BG]). They were compared with patients treated with a standard plan (reference group [RG]). Plans were generated using a simulated annealing inverse planning algorithm. Prospectively recorded urinary, rectal, and sexual toxicities and dosimetric parameters were compared between groups. The study included 120 patients treated with boost technique who were compared with 70 patients treated with a standard plan. Boost technique did not significantly change the number of seeds (55.1/RG vs. 53.6/BG). The intraoperative prostate V150 was slightly higher in BG (75.2/RG vs. 77.2/BG, p = 0.039). Urethra V100, urethra D90, and rectal D50 were significantly lower in the BG. No significant differences were seen in acute or late urinary, rectal, or sexual toxicities. Because there were no differences between the groups in acute and late toxicities, we believe that BV can be planned and delivered to the dominant intraprostatic lesion without increasing toxicity. It is too soon to say whether a boost technique will ultimately increase local control.

Investigation of Shallow Sedimentary Structure of the Anchorage Basin, Alaska, Using Simulated Annealing Inversion of Site Response

Abstract This study deals with shallow sedimentary structure of the Anchorage basin in Alaska. For this purpose, inversion of site response [SR( f )] data in the frequency range 0.5–11.0 Hz from various sites of the basin has been performed using the simulated annealing method to compute subsurface layer thickness, shear-wave velocity ( β ), density, and shear-wave quality factor. The one-dimensional (1D) models for the aforementioned parameters were obtained with preset bounds on the basis of available geological information such that the L -2 norm error between the observed and computed site response attained a global minimum. Next, the spatial distribution of the important parameter β was obtained by interpolating values yielded by the 1D models. The results indicate the presence of three distinct velocity zones as the source of spatial variation of SR( f ) in the Anchorage basin. In the uppermost part of the basin, the β values of fine-grain Quaternary sediments mainly lie in the range of 180–500 m/sec with thickness varying from 15 to 50 m. This formation overlies relatively thick (80–200 m) coarse-grain Quaternary sediments with β values in the range of 600–900 m/sec. These two Quaternary units are, in turn, overlain on Tertiary sediments with β >1000 m/sec located at depths of 100 and 250 m, respectively, in the central and western side along the Knik Arm parts of the basin. The important implication of the result is that the sources of spatial variation of SR( f ) in the Anchorage basin for the frequency band 0.5–11 Hz, besides in the uppermost 30 m, are found to be deeper than this depth. Thus, use of commonly considered geological formations in the depth intervals from 0 to 30 m for the ground-motion interpretation will likely yield erroneous results in the Anchorage basin.

Application of simulated annealing inversion on high-frequency fundamental-mode Rayleigh wave dispersion curves

The simulated annealing (SA) inversion technique has been successfully applied for solving various nonlinear geophysical problems. Following previous developments, we modified the SA inversion, yielding 1D shallow S-wave velocity profiles from high frequency fundamental-mode Rayleigh dispersion curves, and validated the inversion with blind tests. Unlike previous applications of SA, this study draws random numbers from a standard Gaussian distribution. The numbers simultaneously perturb both S-wave velocities and the layer thickness of models. The annealing temperature is gradually decreased following a polynomial-time cooling schedule. Phase velocities are calculated using the reflectivity-transmission coefficient method. The reliability of the model resulting from our implementation is evaluated by statistically calculating the expected values of model parameters and their covariance matrices. Blind tests on two field and 12 synthetic Rayleigh dispersion data sets show that our SA implementation works well for S-wave velocity inversion of dispersion curves from high-frequency fundamental-mode Rayleigh waves. Blind estimates of layer S-wave velocities fall within one standard deviation of the velocities of the original synthetic models in 78% of cases.

Inversion of Seismic Surface Wave Data to Resolve Complex Profiles

For a complex layered site, development of a shear wave velocity profile from inversion of seismic surface wave data can yield nonunique results. One class of solutions provides depth-averaged profiles that are useful but do not detail the local velocity anomalies. Simulated annealing inversion can be used to establish whether nonuniqueness is a concern for a particular case and, if so, focus results to allow a solution that is expected based on independent knowledge of site conditions. A two-step process is recommended whereby the model parameters are first optimized using simulated annealing and then fine tuned by unconstrained linearized inversion. The process also yields useful confidence measures. One example of a complex layered site where the proposed procedure is helpful is a desert profile with high-velocity cemented layers interspersed among uncemented sediments.

Using Triplet Arrays for Broadband Reverberation Analysis and Inversions

Some directional characteristics of observed clutter and reverberation are presented using line arrays with cardioid elements. It is shown that the cardioid arrays break the left/right ambiguity for reverberation sources above ~600-700 Hz. Data analysis uses a cardioid beamforming algorithm developed by researchers at the NATO Undersea Research Centre (NURC, La Spezia, Italy) but the normalization for this algorithm is derived by the author. It is shown that this normalized algorithm has an upper frequency limitation not previously noted. Reverberation data are taken from two recent experiments. One was the 2004 Boundary Characterization Experiment near the Malta Plateau. The area is rich in clutter objects like wrecks and mud-volcanoes and has some subbottom features that may be important. Sources were monostatic coherent pulses and impulsive sources. The receiver was the NURC cardioid array. The other experiment was the U.S. Office of Naval Research's 2003 Geoclutter effort to study shallow-water bottom reverberation and clutter in the STRATAFORM area off New Jersey. Sources were bistatic coherent pulses. The receiver was the five-octave research array (FORA). The STRATAFORM has benign surface morphology but strong clutter is observed. Some highlights of the reverberant returns from that area are discussed that include returns from probable fish schools. From these two data sets, it is shown that up to 15-20-dB left/right discrimination is attainable on broadside cardioid beams in the 1200-1750-Hz region for both linear frequency modulation (LFM) pulses and sound-underwater-source (SUS) broadband data. Also, a (previously developed) constrained simulated annealing (SA) inversion technique is applied to the directional reverberation data from the NURC array. A two-layer fluid model of the bottom is assumed. The algorithm is best at estimating compressional speeds, layer thickness, and attenuations in that order. Extracted bottom parameters at the site are compared with independent inversion results previously reported by Holland. Inverting reverberation from directional arrays is shown to give somewhat better quality results since, unlike standard line arrays, the reverberation data apply to only one bearing along the seafloor.

Po-Thur Eve General-31: Dosimetric Impact of Planning a Boost within a Boost in Permanent Seed Implants

Purpose: To investigate the dosimetric impact on the target volume, boost volume (BV) and urethra of performing limited volume boosts in seed implants. Method and Materials: 35 localized prostate cancer patients with detailed biopsy results were treated with permanent seed implants Personalized plans in which BV corresponding to regions of positive biopsy were generated intra-operatively based on a simulated annealing inverse planning algorithm. The dose objectives are 144 Gy to the prostate with a 3–4 mm margin, 2/3 (1/3) of the prostate covered by 150% (200%) of the prescription dose (PD), urethra V150 less than 10% and D5 should below 220 Gy. Finally, 100% of BV should receive 150% PD (or 216 Gy). Results: Comparing plans without and with BV show no significant change in the number of seeds, needles, prostate V100 and V200. Prostate V150 (D90) show significant differences increasing from 65% (187Gy) to 70% (191Gy). By forcing the coverage of the BV, the 150% isodose lines (which extend outside the prostate) shift inside of the prostate. Small increase in prostate V150 leads to significant increases of the BV V150 from 79% to 94%. BV do not translate to higher urethra doses. Thus multiple seed reconfigurations inside the prostate are achievable to cover BV. Conclusion: Specific areas within the prostate can be boost to receive 150% of the PD with no impact on the urethra. The plans lead essentially to a rearrangement of the seed positions. Potential radiobiological advantages could be obtained at no cost (procedure or time).