# Numerical Simulation of Seismic-Wave Propagation in Specific Layered Geological Structures
## 2 Seismic Event Conditions
### Analysis of Geological Conditions  
The accuracy of a numerical simulation model in earthquake studies is often validated by comparing its results with seismic measurement data [30]. A thorough understanding of the geological parameters within the seismic zone is critical for accurately predicting seismic-wave behavior and assessing potential risk in earthquake-prone areas. This includes geological stratification and the respective density and wave velocities of each layer [31; 32]. To simulate an earthquake with a focal depth of 578 km, it is necessary to consider the geological structure parameters of both the crust and the upper mantle.  
The crust exhibits considerable variation in thickness, with a tendency for greater thickness in continental regions and lesser thickness in oceanic regions. Significant variations are observed across different oceans. For example, the crust is observed to be thinnest at mid-ocean ridges, such as those in the Pacific and Atlantic Oceans [33]. Discontinuities divide the crust into upper and lower layers [34]. The upper stratum is synonymous with the granite rock layer, whereas the lower stratum corresponds to the basalt rock layer [32; 35]. The granite layer, mainly constituted of granite, shows minor variations in its material parameters: density (2.54-2.66 g/cm\({}^{3}\)), porosity (0.1-4.0%), tensile strength (7.00-25.00 MPa), [PERSON]'s modulus (20.0-60.0 GPa), and Poisson's ratio (0.1-0.3). In contrast, basalt, a rock similar in chemical composition to gabbro or diabase, exhibits a wide range of parameters: density (2.70-3.30 g/cm\({}^{3}\)), porosity (0.1-1.0%), tensile strength (10.00-30.00 MPa), Young's modulus (60.0-100.0 GPa), and Poisson's ratio (0.1-0.35) [36].  
The upper mantle encompasses the B layer (Moho surface to \(\sim\)400 km) and the C layer (440 to \(\sim\)960 km). Its average density ranges from 3.2 to 3.6 g/cm\({}^{3}\). The P-wave velocities span from 8.1 to 10.1 km/s, and the S-wave velocities span from 4.4 to 6.4 km/s [37]. Predominantly formed of peridotite, the mantle has a solid rock layer which, together with the crust, forms the rigid lithosphere [38]. The lithospheric mantle averages a depth of 40 to 70 km and a density of around 3.2 g/cm\({}^{3}\). The asthenosphere, located in the upper section of the upper mantle, extends from about 70 km to around 250 km [31]. Given that asthenosphere material is close to its melting point, it is a significant magma source, facilitating local rock melting, with an average density of 3.3 g/cm\({}^{3}\)[39; 40].  
In Northeast China, altitudes vary from 600 to 1400 m in mountainous regions and 50 to 200 m in plains [41]. The average crustal thickness of the area is about 36 km, divided into a 20 km upper crust and a 16 km lower crust [42]. The lithospheric thickness in this region varies from 60 to 70 km, while the asthenosphere ranges from 60 to 220 km [41]. A discontinuity at a depth of 410 km has been highlighted by seismic analysis [17]. For the numerical simulation, the geological structure near the epicenter is defined as follows:  
* Crust: Depth of 36 km. The 20 km granite layer has a geological density of 2.66 g/cm\({}^{3}\), \(V_{p}\) of 5.8 km/s, and \(V_{S}\) of 3.456 km/s. The 16 km basalt layer has a density of 3.3 g/cm\({}^{3}\), \(V_{p}\) of 6.03 km/s, and \(V_{S}\) of 3.73 km/s.
* Lithospheric Upper Mantle: Depth of 24 km with a density of 3.2 g/cm\({}^{3}\), \(V_{p}\) of 8.1 km/s, and \(V_{S}\) of 4.9 km/s.
* Asthenosphere: Depth of 160 km, a density of 3.3 g/cm\({}^{3}\), \(V_{p}\) of 8.14 km/s, and \(V_{S}\) of 5.0 km/s.
* B layer Transition Zone: Depth of 190 km, a density of 3.4 g/cm\({}^{3}\), \(V_{p}\) of 8.8 km/s, and \(V_{S}\) of 5.45 km/s.
* C Transition Zone: Depth of 320 km, a density of 3.6 g/cm\({}^{3}\), \(V_{p}\) of 10.1 km/s, and \(V_{S}\) of 6.26 km/s.