High-density seismic array method has attracted enormous interest in geophysical methods, and it is an advanced seismic observation technology which is of great significance in oil and gas resource detection and underground space exploration. However, designing a portable sensor node that prolongs the lifetime and equips wireless monitoring system to improve construction efficiency has been still a challenge for the high-density seismic array method. In this paper, a portable energy-efficient wireless sensor node and a hybrid communication system that content themselves with complex terrain, large-scale and reliable transmission are proposed to tackle the restrictions of high-density seismic survey. A Wi-Fi communication system based on the star network structure at the core network layer and a ZigBee communication system based on wireless multi-hop structure in the extended network layer form the hybrid communication system. In order to balance the energy of nodes in the extended network and prolong the network lifetime, this paper proposes a multi-hop variable weight routing method (MVWRM). The method selects the cluster-head node and the multi-hop route by changing the weight of the residual energy of the node and the weight of the distance at different periods. Then, a series of simulations and experiments are carried out for verification. The experiments show that the proposed sensor node suggest good performance in equivalent noise level (0.8μV@500Hz, PGA = 1), total harmonic distortion (124dB). Simulation results and performance analysis validate that the effectiveness of the proposed MVWRM can extend about 10% of the node lifetime.

The microtremor survey method (MSM) has the potential to be an important geophysical method for identifying the strata velocity structure and detecting the buried fault structures. However, the existing microtremor exploration equipment has been unable to satisfy the requirements of the MSM, which suffers from low data accuracy, long measurement time, and blind acquisition. In this study, we combined a 2 Hz moving coil geophone with advanced acquisition systems to develop a new integrated energy-efficient wireless sensor node for microtremor exploration. A high-precision AD chip and noise matching technology are used to develop a low-noise design for the sensor node. Dynamic frequency selection technology (DFS) and dynamic power management technology (DPM) are used to design an energy-efficient mode. The data quality monitoring system solves the closed technical flaws between the acquisition systems and the control center via 4G wireless monitoring technologies. According to the results of a series of in situ tests and field measurements, the noise level of the system was 0.7 μV@500 Hz with 0 dB attenuation and 220 mW power consumption of the system in the autonomous data acquisition mode. Therefore, it provides substantial support for the effective data acquisition over long measurement durations in microtremor exploration processes. The applicability of the system is evaluated using field data, according to which the integrated energy-efficient wireless sensor node is convenient and effective for MSM.

Large numbers of seismic channels and high-density energy-efficient acquisition systems are the development trend of seismic instruments and have attracted high R&D interests in recent years. The combination of remote sensing and wireless sensor network technology provides superior observation capabilities for high-density seismic exploration. However, large-scale and multi-node acquisition methods place higher requirements on time synchronization performance. Seismic data with poor time synchronization will cause considerable errors in the interpretation of seismic data and even have no practical significance. Thus, the strict time synchronization performance is the prerequisite and basis for the application of cable-less storage seismograph in high-density seismic array applications. The existing time synchronization methods have high power consumption and poor time synchronization accuracy, which is not suitable for the long-time task. In addition, these methods are affected by the number of nodes and the distance. This paper presents an energy-efficient time-sharing indexed interpolation intercept method for the seismic data synchronization. The time synchronization method uses the high-precision TCXO as the main clock and records GPS time in the SD card at intervals to achieve the high-precision time-stamp for the seismic data. Then the seismic data is intercepted intermittently based on precise time stamps, which achieves the strict seismic data synchronization. Performance analysis shows that the time synchronization accuracy of the proposed method is 0.6 μs and saves 73% energy of the time-sync periods compared to the common GPS timing method. The field measurement results indicate that the time synchronization accuracy is not associated with the working time and the distance between nodes so that the proposed synchronization method is suitable for the high-density seismic survey.

The microtremor survey method (MSM) holds great potential for obtaining subsurface shear wave velocity structures in exploration geophysics. However, the lack of an instant imaging mechanism with local fast computation and processing has become a significant bottleneck hindering the development of MSM. In instant imaging tasks, the computational resources of ordinary nodes employed for imaging are often limited. In this article, we consider a single-point microtremor array network with time-varying wireless channels and stochastic imaging task data arrivals in sequential time frames. In particular, we aim to design an online computation offloading algorithm to maximize the network data processing capability and optimize service quality subject to the long-term data queue stability and average power constraints. We formulate the problem as a the minimum delay problem that jointly determines the binary offloading and system resource allocation decisions in sequential time frames. To address the coupling in the decisions of different time frames, we propose a novel framework named LyECCO that combines the Lyapunov optimization and energy consumption optimization, solve the binary offloading problems with very low computational complexity. Simulation results show the feasibility of the LyECCO, which achieves optimal computation performance while stabilizing all queues in the system.

The large-scale microtremor profiling method (LSMPM) operates under a “distributed data-collection and centralized data-recovery” framework, which has led to significant delays in retrieving shear wave velocity structural information, diminished detection efficacy, and the absence of prompt local computation and processing mechanisms for real-time imaging. Effectively harnessing the computational capabilities of acquisition nodes to facilitate wireless, multinode, low-latency collaborative computing remains a significant challenge. We present a task delay optimization and scheduling algorithm based on modified particle swarm optimization (MPSO) to achieve real-time imaging of shear wave velocity structures at the edge of the sensor network. It enhances the mutation process of the standard particle swarm optimization (PSO), utilizing the delay improvement coefficient as a metric to optimize the delay within computing task queues, thereby avoiding local convergence, augmenting global search capabilities, and consequently reducing the maximum completion time $(\textrm {Makespan})$ of tasks. The MPSO algorithm has undergone extensive simulation testing within the CloudSim environment, and the results indicate that, relative to the PSO task scheduling algorithm, the proposed MPSO task scheduling algorithm reduces the standard deviation of the Makespan by approximately 90%, and when the number of edge servers ranges from 10 to 30, the delay improvement coefficient of the proposed MPSO algorithm can surpass 60%, which underscores the superiority of the MPSO in terms of delay optimization efficacy and algorithmic stability.

High-density seismic array survey has attracted high R&D interest in geophysical methods in recent years, and it is an advanced seismic observation technology which is of great significance in oil and gas resource detection and underground space exploration. However, designing a portable sensor node that prolongs the lifetime and equips wireless monitoring system to improve construction efficiency has been still a challenge. In this paper, a portable energy-efficient wireless sensor node and a wireless communication system that content them with complex terrain, large-scale and reliable transmission is proposed to tackle the restrictions of high-density seismic array survey. This paper proposes a directed diffusion routing method which performs the energy-efficient design by maintaining the link gradient and the ability of automatic power adjustment. In addition, when the sink node initiates an instruction, it quickly covers all nodes and receives the response from the nodes. Then, a series of simulations and experiments are carried out for verification. The experiments show that the equivalent noise of the sensor node is 0.8μV@500Hz, which suggest good performance among the existing sensor nodes. Simulation results and performance analysis validate that the effectiveness of the proposed routing method can maintain the network with only 20mW at autonomous working mode. The field measurement results indicate that the wireless multi-hop energy-efficient system based on the directed diffusion routing method is suitable for the high-density seismic survey.