## 2 Materials and Methods
### Synthetic Model
The seismometer network deployed in the mining facility area (blue triangle) consisted of as many as 41 stations and 14 stations distributed in the off-facilities area (green triangle) (Figure 4). Parameterization of the model is the first step to be performed in seismic tomography calculations [37]. The two most important things in model parameterization are the determination of the grid size and the initial velocity model used. The target study area, station distribution and distribution of microseismic events are the main factors to consider in determining the grid size. In  
Figure 2: Block caving conceptual model which consists of the broken zone, the zone of loosening (yield zone), the seismogenic zone and intact rock (pseudo-continuous domain). areas with high station density and a high number of earthquake events, a relatively small grid size is used. To test the spatial resolution and sensitivity, a CRT was performed. The synthetic model used in this CRT was a chessboard model with a perturbation of \(\pm\)10% of the initial velocity model (Figure 5). The initial velocity model used was a 3D model with a P-wave velocity (Vp) of 5.6 km/s and an S-wave velocity (Vs) of 3.175 km/s, representing typical diorite intrusion rock velocities. The initial velocity model of the CRT was made with an alternate high and low model of 10% relative to the initial model of P- and S-wave velocities. The 3D grid node parameters used were divided into two parts: an inner node and an outer node. The inner node is a node on the inside whose size is more detailed in the research area, while the outer node is on the outside and functions as a coverage with a larger size. The parameters of the inner node were 40 m \(\times\) 40 m \(\times\) 40 m. The size of the outer node was made uniform, with 1.6 km and 3.5 km (the furthest extent) for the nx and ny directions and 2.5 km for the nz direction. Synthetic travel time data obtained via the forward modeling process using the CRT velocity model were calculated using the location of the hypocenter and station. To obtain absolute velocity data in this study, the forward modeling process and, for inversion, the TomoDD program created by [PERSON] (2000) and developed by [PERSON] and [PERSON] (2006) were used. The results of the forward modeling were synthetic absolute travel times of P- and S-waves. The P and S travel times were then extracted to obtain the input phase format for pairing events using the ph2 dt program. As the data used were synthetic, all the absolute travel times of P- and S-waves were recorded by all stations. To represent real seismic observational conditions, random sorting of phase travel time data was carried out with a limit of 1 earthquake event recorded by a minimum of 10 closest stations. We calculated the direction of propagation of the wave rays and calculated the travel time using the pseudo-bending ray-tracing algorithm. The results of the ray tracing from the forward modeling gave the raypath and calculated travel time (t\({}_{\text{cal}}\)) of wave propagation along the trajectories of P- and S-waves. The results for the ray tracing of P- and S-waves can be seen in Figure 6.  
Figure 3: Conceptual caving model, showing the abutment zone, seismogenic zone and microseismic event distribution. Figure 4: Distribution map of the station network showing the mining facilities (blue triangles) and the distribution of the off-facilities area station network (green triangles). The black dots indicate the distribution of earthquake events, and the cave is indicated by a black triangle. Figure 5: Checkerboard Resolution Test Model, with perturbation \(\pm\)10% of the initial velocity model. Figure 6: (a) Raypath following the facility (red triangles). (b) Raypath in the off-facilities area (blue triangles). The synthetic Vp and Vs data were then grouped based on time, event and number of recording stations to be made in phase format as inputs to the ph2 dt program.