Earthquake disasters cause serious losses of human life and property. A rapid response platform for earthquake disasters can provide scientific suggestions for real-time postearthquake rescue deployment, reducing losses. We developed an earthquake response platform named CGFDM3D-EQR that quickly provides earthquake intensity for evaluating complex earthquake disasters. The intensity evaluations are derived from strong ground motion simulations that couple 3D complexities in elevation, medium structure, and earthquake source. The curved grid finite difference method (CG-FDM), which can accurately resolve 3D complexities during earthquake simulation, is adopted in this platform. We developed a CG-FDM parallel algorithm for strong ground motion simulation based on central processing unit (CPU) and graphical processing unit (GPU) heterogeneous architectures. With these characteristics, the platform can simulate strong earthquake ground motions and provide seismic intensity assessments in less than 30 min using our cluster. To verify the platform, we performed four simulations, and the results show that our platform is reliable and efficient. Owing to its user-friendly features and high efficiency, the CGFDM3D-EQR platform can play essential roles in seismic hazards responses, scenario earthquake evaluations, and related applications.

A high-scalable and fully optimized earthquake model is presented based on the latest Sunway supercomputer. Contributions include: 1) the curvilinear grid finite-difference method (CGFDM) and flexible model applying perfectly matched layer (PML) and enabling more accurate and realistic terrain descriptions; 2) a hybrid and non-uniform domain decomposition scheme that efficiently maps the model across different levels of the computing system; and 3) sophisticated optimizations that largely alleviate or even eliminate bottlenecks in memory, communication, etc., obtaining a speedup of over 140×. Combining all innovations, the design fully exploits the hardware potential of all aspects and enables us to perform the largest CGFDM-based earthquake simulation ever reported (69.7 PFlops using over 39 million cores). Based on our design, the Turkey earthquakes (February 6, 2023), and the Ridgecrest earthquake (July 4, 2019), are successfully simulated with a maximum resolution of 12-m. Precise hazard evaluations for the hazardous reduction of earthquake-stricken areas are also conducted.

SUMMARY: For simulating the dynamic rupture process in earthquake scenarios, the stress distribution along the fault remains unclear owing to a lack of direct measurements. Regional stress fields are often resolved onto the fault plane to determine the stress distribution along it. To overcome this limitation, we considered different interseismic locking models to better constrain the actual stress distribution. Specifically, we took the Suoerkuli section in the middle of the Altyn Tagh fault, China, and conducted dynamic rupture simulations to obtain possible earthquake scenarios. The surface rupture length and moment magnitude obtained from the simulations were consistent with those of historical earthquakes. Compared with the traditional stress field resolution method, our approach led to better constrained fault rupture extent and distribution characteristics of regional intensity, thereby avoiding overestimations of earthquake damage. We conclude that examining regional seismic hazards and risks based on seismic dynamic rupture simulations that account for the locking ratio of the fault plane is advantageous, and should be encouraged.

High-resolution three-dimensional (3D) seismic simulation imposes severe demands for computational memory, making low-storage seismic simulation particularly important. Due to its high-efficiency and low-storage, the half-precision floating-point 16-bit format (FP16) is widely used in heterogeneous computing platforms, such as Sunway series supercomputers and graphics processing unit (GPU) computing platforms. Furthermore, the low-storage Runge-Kutta (LSRK) technique requires lower memory resources compared with the classical Runge-Kutta. Therefore, FP16 and LSRK provide the possibility for low-storage seismic simulation. However, the orders of magnitude of the physical quantities (velocity, stress, and Lamé constants) in the elastic wave equations are influenced by the P-wave and S-wave velocities and the densities of the elastic media. This results in a huge order of magnitude difference between the stored velocity and stress values, which exceed the range of the stored values of FP16. In this paper, we introduce three dimensionless constants, C_v, C_s, and C_p, into elastic wave equations, and new elastic wave equations are derived. The three constants, C_v, C_s, and C_p, keep the orders of magnitude of the velocity and stress at a similar level in the new elastic wave equations. Thus, the stored values of these variables in new equations remain within the range of the stored values of FP16. In addition, we introduce the use of the LSRK due to its low-storage characteristic. In this paper, based on the FP16 and LSRK low-storage techniques, we develop 3 optimized multi-GPU solvers for seismic simulation using the curved grid finite-difference method (CGFDM). Moreover, we perform a series of seismic simulations to verify the accuracy, stability, and validity of the optimized solver coupled with the two techniques. The verifications indicate that through maintaining the calculation accuracy, the computational efficiency of the solver is significantly optimized, and the memory usage is remarkably reduced. In particular, under the best conditions, the memory usage can be reduced to nearly 1/3 that of the original CGFDM solver.

The 2022 $Mw$ 6.6 Luding earthquake occurred on the Xianshuihe fault, one of China’s most active faults. Revealing the rupture process of the Luding earthquake and exploring the distribution of high intensities is important for earthquake hazard reduction around the active Xianshuihe fault in the future. Therefore, we modeled the dynamic rupture and ground motions of the Luding earthquake. The dynamic rupture modeling demonstrates that the maximum slip of the fault plane is ∼1.34 m, and the ground‐motion simulations show the highest intensity attained is IX. In addition, we conducted a comparative analysis between synthetic data and station observation records, illustrating that our simulation results are compatible with the seismic station observations. We investigated the influence of geometric complexities on the Xianshuihe fault rupture and found that varying the dip angle of the southern segment may lead to premature rupture termination and constrain the rupture propagation. Our study provides insights into the complex geometry’s effect on the physical process of large earthquakes on the Xianshuihe fault.