Traveltime Computation Research Articles

Seasonal biodegradation of the artificial sweetener acesulfame enhances its use as a transient wastewater tracer

The persistence of the artificial sweetener acesulfame potassium (ACE) during wastewater treatment and subsequently in the aquatic environment has made it a widely used tracer of wastewater inputs to both surface water and groundwater. However, the recently observed biodegradation of ACE during wastewater treatment has questioned the validity of this application. In this study, we assessed the use of ACE not only as a marker of wastewater, but also as a transient wastewater tracer that allows both the calculation of mixing ratios and travel times through the aquifer as well as the calibration of transient groundwater flow and mass transport models. Our analysis was based on data obtained in a nearly 8-year river water and groundwater sampling campaign along a confirmed wastewater-receiving riverbank filtration site located close to a drinking water supply system. We provide evidence that temperature controls ACE concentration and thus its seasonal oscillation. River water data showed that ACE loads decreased from 1.5–4 mg·s−1 in the cold season (December to June; T<10 °C) to 0–0.5 mg·s−1 in the warm season (July to November; T>10 °C). This seasonal variability of >600% was detectable in the aquifer and preserved >3 km, with ACE concentrations oscillating between <LOQ in the warm season up to 1 μg·L−1 in the cold season. The large seasonal variation in ACE concentrations during wastewater treatment, compared to the other sweeteners (sucralose, cyclamate, and saccharin) and chloride enables its use as a transient tracer of wastewater inflows and riverbank filtration. In addition, the arrival time of the ACE concentration peak can be used to estimate groundwater flow velocity and mixing ratios, thereby demonstrating its potential in the calibration of groundwater numerical models.

Calculation of Theoretical Travel Time and Automatic Picking of Actual Travel Time in Seismic Data

We used the ray tracing technique based on the IASP91 Earth model to calculate the travel times in order to identify the phases. This technique can calculate the travel times for the seismic phases in the conventional travel time tables. The waveform data received from the stations in the Guangxi area are selected for analysis and discussion. The outcomes of the numerical modeling and its use demonstrate that there is good agreement in terms of the absolute differences between the calculated and theoretical travel times from the ISAP91 tables. The relative residuals are determined directly from the actual arrival times picking during the correlation analysis, and the validity of the travel time method for picking seismic phases by correlation analysis can be demonstrated.

Fast 3D “wave-consistent” ray tomography based on a polynomial representation of a model

In the paper, we describe an original 3D travel-time tomography approach. It is based on the new realization of the bending method which to some extent takes into account the band-limited nature of real seismic signals propagation. As a result, two-point ray tracing provides more reliable ray trajectories and travel times in complex media. Another original feature of the proposed tomography is that the model is represented using the Chebyshev polynomials. Such parameterization allows analytical calculation of travel times and their derivatives with respect to model parameters and significantly reduces the number of parameters to be recovered during inversion compared to more common grid tomography. In certain situations, the proposed approach provides significant computational advantages. Numerical examples prove its efficiency.

СУЩЕСТВУЮЩИЕ МОДЕЛИ ОРГАНИЗАЦИИ МАРШРУТОВ СКОРОСТНОГО ОБЩЕСТВЕННОГО ТРАНСПОРТА И ИХ ВЛИЯНИЕ НА ВРЕМЯ ПОЕЗДКИ ПАССАЖИРА

Currently, there are no studies in the Russian scientific literature devoted to models of the organization of high-speed passenger transport routes. At the same time, as practice proves, the time of movement of passengers significantly depends on the accepted system of organization of routes. For example, non-stop routes, on the one hand, increase the required volume of rolling stock used for passenger transportation, but, on the other hand, reduce the total transshipment time. The article analyzes approaches to the organization of routes on the high-speed passenger transport network and presents the calculation of the overhead travel time of passengers for different network options. Calculations of the passenger’s traffic speed are given separately, depending on the distance of a trip and the type of transport used. It is pointed out that the optimal choice of the model of the route network of urban passenger transport makes it possible to reduce the cost of infrastructure construction and improve the quality of public services.

INFLUENCE OF TRAVEL TIME ON INFANT MORTALITY RATE IN BALI PROVINCE, INDONESIA

Infant mortality rate was still a problem in Indonesia, especially in Bali Province. It might be caused by many factors, and travel time as one of the factors influenced it. Travel time was chosen to model physical geographic access because it is a better measure that incorporates elevations, road network, and travel speed among other factors that influence geographic accessibility compared to network and straight-line distance. This study aimed to assess the influence of travel time to primary health care (PHC) on infant mortality rate in Bali Province. The method used was used GIS processing with AccessMod 5 as WHO open-source application to calculate travel time; for statistics, we used bivariate correlation and multivariate linear regression, both processed by JASP as open-source statistic application from Amsterdam University. The results show a bivariate model where child mortality correlated very strongly and backward with travel time of 15 min (r = -0.81; 95% CI -1 to -0.42 p 0,00439), 30 min (r = -0.80; 95% CI -1 to -0.40 p 0.008), 60 min (r = -0.75; 95% CI -1 to -0.29 p 0.01), 90 min (r = -0.63; 95% CI -1 to -0.07 p 0.03). The best multivariate model was travel time of 15 min (y = 8.47-0,29*tt15) if assumed as a single factor. Travel time to the PHC influenced infant mortality rate. The shortest travel time to the PHC of up to 90 min will decrease the infant mortality rate in Bali Province as an effort to decrease infant mortality rates involves ensuring that every pregnant woman has convenient access to nearby healthcare facilities. Keywords: Infant Mortality, Travel Time, Regression DOI： https://doi.org/10.35741/issn.0258-2724.58.3.45

Methodology for creating dynamic emergency vehicle availability maps

Abstract One of the main priorities of emergency services is to minimize the response time to calls. In the process of proper allocation of emergency vehicles, maps of emergency vehicle accessibility are found to be helpful. These maps represent areas within which emergency services can reach the specified location within a certain time. Calculating travel times requires taking into account the rapidly changing current road conditions. This paper presents a method for dynamically generating maps of emergency vehicle accessibility, considering network models and irregular computational grids.

A Bi-Objective Lane Reservation Problem Considering Dynamic Traffic Flow

Lane reservation strategies are widely used to ensure the right of way for eco-friendly vehicles and encourage people to green their commute. In most lane reservation problems (LRPs), the parameters underlying the system traffic conditions (e.g., vehicle speed and traffic flow) cannot be effectively specified. This paper addresses a new dynamic lane reservation problem (DLRP), which aims to optimize lanes that need to be reserved in different time periods based on trajectory data for existing transit network optimization. For passengers in reserved lanes, their travel time is minimized to guarantee traffic priority. Considering that the reserved lanes cause travel time growth on regular lanes, an improved multiobjective mixed integer nonlinear programming (MINLP) is established to minimize the delay. The problem complexity of this paper is NP-hard. This paper applies a preprocessing method for the actual traffic flow data analysis for link travel time calculation. We developed a hybrid evolutionary algorithm decomposing a multiobjective optimization problem (MOP) to a collection of simple MOPs. These subproblems are collaboratively solved. The hybrid crossover strategy exploits the advantages of different crossover operators for a better performance. The experimental results of MOEA/D and NSGA-II with standard test functions show that the proposed algorithm can improve the convergence and distribution of the results. Through numerous analyses and calculations of instances, the proposed algorithm is proven to be effective.

An efficient hybrid mesh method for seismic traveltime computation with irregular surfaces

Accurate and efficient traveltime computation with irregular surfaces is a prerequisite for traveltime tomography, seismic location, and seismic exploration in mountainous areas. The eikonal equation method is computationally favourable and has gained increasing popularity for obtaining traveltime in recent years. Nowadays most algorithms that can solve eikonal equation with irregular surfaces are based on fully unstructured triangular mesh or surface-fitting mesh. However, these methods have poor performance in terms of computational cost and accuracy. To cope with this problem, we develop a hybrid mesh method based on fast-sweeping-based eikonal solver with rectangular and unstructured triangular mesh for obtaining traveltime with irregular surfaces. In other words, we propose to divide the model into several different regions, which are discretized by rectangular mesh and unstructured triangular mesh respectively. Near the irregular surfaces of model, we use fast sweeping method based on unstructured triangular mesh which releases the full potential of unstructured triangular mesh’s flexibility in accurately describing the irregular geometry of computation domain. For the rest part of the model, we adopt rectangular mesh to make full use of high efficiency of the corresponding high-order fast sweeping algorithm. At the interface of two types of mesh, we need interpolate the known nodes’s traveltimes to get the boundary condition of another mesh, so as to start the fast sweeping method therein. It is found that the accuracy of hybrid mesh method can be increased by 83%, the computation time is reduced by 72%, and the storage requirement is reduced by 72%, compared with the fast sweeping method with full triangular mesh, when the rectangular mesh proportion is 80% in our model. Therefore, this proposed hybrid mesh method can greatly enhance the computational efficacy and serve as an potential forward engine in seismic inversions.

Modelling geographic access and school catchment areas across public primary schools to support subnational planning in Kenya

ABSTRACT Understanding the location of schools relative to the population they serve is important to contextualise the time, students must travel and to define school catchment areas (SCAs) for planning. We assembled a spatio-temporal database of public primary schools (PPS), population density of school-going children (SGC), and factors affecting travel in 2009 and 2020 in Kenya. We combined the assembled datasets within cost distance and cost allocation algorithms to compute travel time to the nearest PPS and define SCAs. We elucidated travel time and marginalised SGC living outside 24-minutes, government's threshold at sub-county level (decision-making units). Weassembled 2170 PPS in 2009 and 4682 in 2020, an increase of 115.8%, while the average travel time reduced from 28 to 17 minutes between 2009 and 2020. Nationally, 65% of SGC were within 24-minutes’ catchment in 2009, which increased to 89% in 2020. Subnationally, 19 and 61 out of 62 sub-counties had over 75% of SGC within the same threshold, in 2009 and 2020, respectively. Findings can be used to target the marginalised SGC, and monitor progress towards attainment of national and Sustainable Development Goals. The framework can be applied in other contexts to assemble geocoded school lists, characterise travel time and model SCA.

Modeling Accessibility to Emergency Obstetric Care in Mountain Region on Adonara Island, Eastern Indonesia

The geographical conditions of an area influence accessibility problems. The difficult geographical conditions caused travel time to the location of the obstetric emergency center to be very long. One of the causes of the high maternal mortality rate in Eastern Indonesia is the long time to travel to Basic Emergency Obstetrics Cares. This study aims to model the travel time to the PONED-Pelayanan Obstetri Neonatal Emergensi Dasar (Basic Emergency Obstetric and Neonatal Care-BEmONC) in a mountain region. The difficulties in access to obstetric care could cause maternal mortality in mountain regions. This study was done on the island of Adonara in the Flores Timur district. Adonara Island has a high maternal mortality rate. Modeling accessibility used a raster-based model to model travel time. The data used Landsat 8 imagery, Digital Elevation Model (DEM), and road network data to obtain a land cover layer. The Saga GIS travel time calculation tool is used to calculate the accumulated cost of travel time. The cost is based on the speed of travel through each land cover pixel to the location of the Puskesmas Waiwerang (PONED 1) and Puskesmas Waiwadan (PONED 2). The results of the travel time modeling show that people living in five sub-districts reach the two PONED locations in ≥ 1 hour. The longest time for people to travel to PONED is ≥ 6 hours from Ile Boleng sub-district because there is a mountain in the Ile Boleng sub-district. The scenario of adding one PONED shows that only people living in two sub-districts reach the PONED ≥ 1 hour. This spatial modeling of travel time to the location of the PONED (emergency obstetric care) can be used by local governments in eastern Indonesia to improve access to the location of basic obstetric emergency health centers in mountain areas.

An Algorithm of Acoustic Emission Location for Complex Composite Structure

Acoustic emission (AE) is widely used in engineering and rock mechanics. The algorithm of AE location based on homogeneous medium or single velocity structure is confronted with lower accuracy when it is applied to the actual working conditions that are prevailing complicated and heterogeneous. In this paper, an AE location algorithm based on complex composite structure (CCS) is proposed via carrying out the following studies: (1) A new travel time calculation scheme suitable for CCS with step-like velocity change is proposed based on an optimized shortest path algorithm. By doing this, a reasonable ray path that is only deflected at the interface is obtained to improve the travel time accuracy. The time complexity of the new algorithm is O(nlog2n). (2) The availability of the new algorithm is verified via a theoretical analysis under a one-dimensional velocity structure as well as an AE experiment using a complex structure under artificial excitation. (3) The AE location during the failure of a simulated CCS in the laboratory indicates that the new algorithm can effectively calculate the travel time and ray path of the sample.

P-, SV- and SH-wave eikonal approximations for HTI media based on perturbation theory

SUMMARY The eikonal equation for transversely isotropic media is a complex quartic partial differential equation that causes instability in traveltime inversion. The phenomenon of shear wave splitting in a transversely isotropic model with a horizontal symmetry axis (HTI) provides information for inversion. However, the involvement of shear waves makes the computation of forward modelling and inversion more time-consuming than when only using Pwaves. Most studies of traveltime approximation based on the eikonal equation are based on an acoustic assumption, which does not work for shear waves. Therefore, based on perturbation theory, we derive approximate solutions of the eikonal equation in a heterogeneous elastic HTI model for P, SV and SH waves to improve the traveltime computation efficiency. The approximate solutions of linear, quadratic and Shanks forms are based on the linearization of the traveltime function in terms of fracture weaknesses in an isotropic background, which are suitable for joint P-, SV- and SH-wave traveltime inversion and tomography for fracture parameters. When applied for a homogenous model, the proposed formulation results in a simple and accurate traveltime approximation. The first- and second-order perturbation coefficients are used to analyse the sensitivity of the traveltime to fracture weakness. To improve the accuracy of our approximation, we also expand the approximation of the P-wave traveltime with respect to the anellipticity parameter η in an elliptic background, which is evaluated by performing an error test. Based on the accuracy and stability of the perturbation, we select a set of linear equations with respect to the fracture weaknesses and a set of more accurate nonlinear equations to serve different needs.

Distance to Multidisciplinary Team Clinic in Gaborone, Botswana, and Stage at Cervical Cancer Presentation for Women Living With and Without HIV.

Cervical cancer is the leading cause of cancer death for women in Botswana. Barriers in access to cancer care can lead to later stages at diagnosis and increased mortality. This study evaluated access, defined as travel time from a patient's residential village to a multidisciplinary team clinic in Gaborone, with stage of cervical cancer at presentation. In addition, because of the high HIV prevalence in Botswana, we explored the association between travel time and HIV status. Eligible patients with cervical cancer presenting to the multidisciplinary team between 2015 and 2020 were included. Data were abstracted from questionnaires and hospital records. Google Maps was used to calculate travel time. Multinomial regression was used to examine travel time and cancer stage, and multivariable logistic regression was used to investigate travel time and HIV status. We identified 959 patients with cervical cancer of which 70.1% were women living with HIV. The median travel time was approximately 2 hours. Using a reference group of stage I disease and a travel time of < 1 hour, the odds of presenting with stage II increased for patients traveling 3-5 hours (adjusted odds ratio [OR], 2.00; 95% CI, 1.14 to 3.52) and > 5 hours (OR, 2.19; 95% CI, 1.15 to 4.19). There were no significant associations for stage III. For stage IV disease, the odds were increased for patients traveling 3-5 hours (OR, 2.93; 95% CI, 1.26 to 6.79) and > 5 hours (adjusted OR, 4.05; 95% CI, 1.62 to 10.10). In addition, the odds of patients presenting living with HIV increased with increasing travel time (trend test = 0.004). This study identified two potential factors, travel time and HIV status, that influence access to comprehensive cervical cancer care in Botswana.

The Impact of Telemedicine on Indirect Patient Costs in an Outpatient Radiation Oncology Department

Purpose/Objective(s)Patients incur more than medical-related expenses when attending necessary consultation and follow-up visits, including time and travel costs. With the rapid integration of telemedicine in response to the COVID-19 pandemic, our department gained another tool that has the potential to reduce the financial burden of cancer care for our patients. The aim of this study was to estimate the indirect cost savings (time, travel costs, opportunity costs) resulting from the use of telemedicine at a large, academic radiation oncology outpatient clinic located in a densely populated suburban setting. We hypothesize that telemedicine provides time- and cost-savings for patients.Materials/MethodsAll telemedicine and in-person visits scheduled at our main outpatient clinic over a one-week period in June 2021 were retrospectively reviewed. Care visits with patients residing outside of the state were excluded. Travel distance and time calculations were estimated using Google Maps and based on patients’ reported home address. Travel cost was calculated using the IRS 2021 standard mileage rate of $0.56 per mile. Opportunity cost was calculated by multiplying round-trip travel time with estimated hourly wage, derived by median household income per census block group and in the context of a 40-hour work week. Annual projections were calculated by multiplying weekly cost savings by 52.ResultsA total of 156 patients had scheduled visits in our department over one week, 115 of which were via telemedicine. There was no difference in gender, race, ethnicity, and insurance status between telemedicine and in-person visits. Those attending telemedicine vs in-person visits were younger in age (61 vs 68 yrs, p=0.03). There was no significant difference between distance or time traveled to the cancer center between telemedicine and in-person cohorts. For telemedicine visits, median per-visit round-trip travel time saved was 66 minutes (IQR, 39-168 minutes) with a travel cost savings of $33.60 (IQR, $17.92 - $100.80), opportunity cost savings of $67.04 ($42.97 - $118.56), and overall cost savings of $110.57 (IQR, $59.94 - $202.04). Annually, telemedicine visits are estimated to save patients a total travel time of 12911.6 hours, travel costs of $402,684, opportunity costs of $530,588, and overall cost savings of $933,272.ConclusionTelemedicine benefits patients with time- and cost-savings in an outpatient radiation oncology clinic. Our estimates are likely under-representative of the entire financial impact, as costs related to childcare, parking, tolls, hotels, and meals were not captured in our analysis. These unmeasured costs are likely amplified for those patients who live further from the clinic. Despite this, travel distance was not associated with utilization of telemedicine. In clinically appropriate situations, patient-centered metrics such time- and cost-savings should be considered when informing the choice between telemedicine and in-person visits.

Fast iterative method for seismic wave travel time calculation under undulating surface conditions

Seismic wave travel time is an important seismic attribute information and is widely used in various seismic forward and inversion methods, including seismic migration imaging, seismic tomography, seismic wave forward modeling and other core seismic data processing methods. The accuracy and efficiency of the travel time algorithm are important for the above methods. In the practical application of seismic exploration, it is often carried out under the condition of undulating surface, which has a significant impact on the travel time calculation. Therefore, it is of great significance to study an efficient and high-precision travel time calculation method that can adapt to undulating surface condition. In this paper, Fast iterative method (FIM) is modified to a topography travel time calculation method. The method employs an iterative method to solve the equation of function to obtain seismic wave travel time by maintaining a narrow band called the active list, and the algorithm can update all grid nodes in the active list at a time. We will verify the travel time computing power of the FIM method through several different velocity models.

Elastic anisotropic finite-difference full-wave modeling and imaging of 2D tilted transversely isotropic (TTI) media

Imaging below the tilted transversely isotropic (TTI) media pose serious problems and distortions of the subsurface geological targets of interest for hydrocarbon exploration, which is very common in fold-thrust belts or active tectonic areas like the Rocky Mountain foothills of the Canada or foothills of the Himalaya. To model and image below the TTI media having symmetry axis orthogonal to dipping anisotropic layers, a 2D TTI thrust sheet is considered for elastic anisotropic finite-difference full-wave modeling and generation of synthetic seismic data using the robust staggered-grid scheme of wave propagation. Free-surface boundary conditions at the top and absorbing boundary conditions for the other three sides of the model have been imposed to reduce undesirable edge effects and suppress dispersions. The synthetic seismic data generated for the 2D TTI thrust model are migrated using the anisotropic Kirchhoff pre-stack time (PSTM) and depth migration (PSDM) technique followed by the migration velocity analysis (MVA) algorithm. The traveltime computations are made using robust eikonal equations with fourth-order elastic anisotropic finite-difference solutions to handle large tilts (ν) along with anisotropic ray-tracing to image below the TTI thrust sheet. The MVA algorithm adopted also estimates the anisotropic parameters ε and δ accurately within the acceptable error limit through successive iterations of inversion and parameter update, which results in sufficient flattening of the reflection events in the common image gathers (CIGs). This is a powerful and stable methodology to handle large tilt (ν = 60°) of the steeply dipping reflectors in complex geological structure like the TTI thrust model without much distortion of CIGs for which the symmetry axis of each TTI block is set orthogonal to the bottom of the reflectors having different tilts.

Influence of shear wave velocity heterogeneity on SH-wave reverberation imaging of the mantle transition zone

SUMMARY Long-period (T &amp;gt; 10 s) shear wave reflections between the surface and reflecting boundaries below seismic stations are useful for studying phase transitions in the mantle transition zone (MTZ) but shear-velocity heterogeneity and finite-frequency effects complicate the interpretation of waveform stacks. We follow up on a recent study by Shearer &amp; Buehler (hereafter SB19) of the top-side shear wave reflection Ssds as a probe for mapping the depths of the 410-km and 660-km discontinuities beneath the USArray. Like SB19, we observe that the recorded Ss410s-S and Ss660s-S traveltime differences are longer at stations in the western United States than in the central-eastern United States. The 410-km and 660-km discontinuities are about 40–50 km deeper beneath the western United States than the central-eastern United States if Ss410s-S and Ss660s-S traveltime differences are transformed to depth using a common-reflection point (CRP) mapping approach based on a 1-D seismic model (PREM in our case). However, the east-to-west deepening of the MTZ disappears in the CRP image if we account for 3-D shear wave velocity variations in the mantle according to global tomography. In addition, from spectral-element method synthetics, we find that ray theory overpredicts the traveltime delays of the reverberations. Undulations of the 410-km and 660-km discontinuities are underestimated when their wavelengths are smaller than the Fresnel zones of the wave reverberations in the MTZ. Therefore, modelling of layering in the upper mantle must be based on 3-D reference structures and accurate calculations of reverberation traveltimes.

Estimation of travel time variation caused by transport infrastructure development

Purpose The expected benefits of newly developed transportation infrastructures are the saving of travel time and further promoted transport economics. There is a need for a methodology of travel time estimation with acceptable robustness and practicability. Macroscopic fundamental diagram (MFD) represents the overall traffic performance at a network level by linking average flow, speed and density. MFD can be used to estimate network state and to describe various traffic management strategies. This study aims to describe the effect of new infrastructure development on the network performance using the MFD framework. Design/methodology/approach The scenarios of Islamabad Road network before and after the infrastructure construction were simulated, in which the floating car data set (FCD) for multiple modes was extracted. MFD has been formed for the whole region and partitioned region, which was divided on the basis of infrastructural changes. Moreover, this study has been extended to calculate travel time for multiple modes using the MFD results and the Bureau of Public Roads (BPR) function at a neighborhood level. Findings MFD results for the whole network showed that the speed of traffic improves after the construction of new infrastructure. The travel time estimates using MFD results were dependent on the speed estimates, whereas the estimates obtained using the BPR function were found to be dependent on the traffic volume variation during different intervals of the day. By using the FCD for multiple modes, travel time estimates for multiple modes were obtained. The BPR function method was found valid for estimating travel time of traffic stream only. Originality/value This paper innovatively investigates the change in network performance for pre-construction and post-construction scenarios using the MFD framework. In practice, the approach presented can be used by transportation agencies to evaluate the effect of different traffic management strategies and infrastructural changes.

A fast space-time-domain Gaussian beam migration approach using the dominant frequency approximation

The Gaussian beam migration (GBM) is a steady imaging approach, which has high accuracy and efficiency. Its implementation mainly includes the traditional frequency domain and the recent popular space-time domain. Firstly, we use the upward ray tracing strategy to get the backward wavefields. Then, we use the dominant frequency of the seismic data to simplify the imaginary traveltime calculation of the wavefields, which can cut down the Fourier transform number compared with the traditional GBM in the space-time domain. In addition, we choose an optimized parameter for the take-off angle increment of the up-going and down-going rays. These optimizations help us get an efficient space-time-domain acoustic GBM approach. Typical four examples show that the proposed method can significantly improve the computational efficiency up to one or even two orders of magnitude in different models with different model parameters and produce good imaging results with comparable accuracy and resolution with the traditional GBM in the space-time domain.

Seismic Tomographic Modeling of the Crust and Upper Mantle beneath Israel and the Middle East: Improved Resolution through Optimized Model Parameterization

ABSTRACT Accurate regional seismic travel-time (RSTT) predictions rely on regional phases (e.g., Pg, Lg, Pn, Sn) to account for 3D effects in the crust and upper mantle that are not captured by 1D models traditionally used for real-time location. The RSTT prediction model accounts for regional-scale crust and upper mantle structure globally by incorporating regional seismic phases into its travel-time calculations. Previous versions of the RSTT model have used a constant grid cell size of 1°. To improve the tomographic accuracy of recovering velocity structure at regional scales, we perform data-driven grid refinement on the RSTT model down to a 0.125° grid (∼14 km) in pursuit of two main goals: (1) to test the limits of RSTT capability and accuracy of determined velocity structure through variable grid refinement and (2) to image smaller structures in Israel and the Middle East and illuminate upper mantle dynamics operating in this complex tectonic area. We investigate the effects of model parameterization as grid cell size decreases and the trade-offs between recovered velocity structures. Our final dataset includes 4751 events and 499 stations that recorded 79,344 Pn and 7489 Pg. The variable grid refinement method allows recovery of finer-scale velocity structures and reduces travel-time residuals in areas with the highest data coverage. At smaller grid cell sizes, longer paths need to be upweighted to stabilize the inversion. Results illuminate tectonic features undefined in coarser grid-size models; in particular, we observe mantle perturbations related to the subduction zone around the Cyprian arc and crustal anomalies near the Dead Sea fault and throughout the Anatolian plate.