| Shallow high-resolution seismic reflection exploration is attractive but still a hot nut to crack for its complexity, especially in bad seismic conditions such as minerals survey, environmental geologic investigation and so on. High-resolution seismic exploration is a systemic project, and the rule of high-resolution exploration must be followed by bestir of seismic wave, arrangement of geophones, collection of data, process and explanation of data. Electro-magnetic vibrator is a new type of non-destructive vibroseis which frequency is adjustable. Its design ideas come from radar and sonar echo ranging technology, and its applications were mainly located in the shallow high-resolution seismic exploration. It not only can enhance the high frequency components by nonlinear sweep in accordance with the pre-determined frequency, but also could achieve the desired amplitude spectrum by variable frequency sweep. Compared with hydraulic vibrator, the electro-magnetic vibrator was characterized by high output frequency, but its output power was relatively smaller, hence the needed sweep time was longer. The corresponding seismic data acquisition system (seismic instruments) should have a higher sampling rate and a longer record time because of the above-mentioned characteristics of electro-magnetic vibroseis. The present seismic instruments have limitations when used with the electromagnetic vibroseis, such as sampling rate, record time and data transmission rate, which limits the application of electromagnetic vibrator. The dissertation, which was supported by the state 863 project "Study on underground vibroseis phased array imaging technology", aims to design a suitable seismic data acquisition system. The dissertation focus on the distributed seismic data transmission technology and the main work and conclusions are as follows:1. The composition and structure of present seismic instruments were compared and the advantage of the telemetry seismic instruments was analyzed. Due to the limitations of centralized structure, traditional seismic instruments were difficult to adapt to the requirements of multi-channel, high sampling rate and high signal-to-noise ratio in seismic exploration. In telemetry seismic instruments which adopted the distributed structure, the collection points were moved from the trunk to near the geophone, which was a better solution of the above problem. Distributed framework is therefore the development trend of seismic instruments. The key issue of telemetry seismic instruments in which distributed structure was adopted was how to transfer the seismic data to the host, which was also an important technical specification of telemetry seismic instruments. The earthquake measured how fast and reliable transmission of data to the mainframe is the need to address key issues an important instrument for measuring seismic indicators. Therefore distributed data transmission technology is the key technologies, which leads to the focus of this study.2. To find a reliable and efficient seismic data transmission technology, the wide used Ethernet technology in computer network and fieldbus technology were studied. The present industrial fieldbus standards were different from each other and it is difficult to make one Uniform standard. In recent years, the Ethernet which was based on TCP/IP has gradually been applied in the industrial field due to its characteristics of open structure, cheap and high-speed. A method of distributed seismic data transfer based on Ethernet was presented in allusion to the characteristics of electromagnetic vibroseis, in which the successful experiences of industrial Ethernet were referred. A relay network topology was also given based on the construction feature of actual seismic exploration. From the point of view of transmission rate, the present widely used 100M Switched Ethernet could meet the need of huge amounts of data transmission in seismic exploration based on electro-magnetic vibroseis. On the other hand, the relay network resolved the problem of Ethernet when used in the field such as wiring.3. Dynamic IP and routing table management in relay Ethernet topology were studied. In the actual electromagnetic vibroseis exploration, the multiple cover technologies were adopted and the collection points should be moved, so the relative position of each acquisition station is not fixed. Therefore, it is not appropriate to set up a fixed IP address for each acquisition station. The traditional dynamic IP allocation method (DHCP) was not applicable to relay network topology. A dynamic IP allocation method based on UDP broadcast was presented in which each station was given an IP address in accordance with the corresponding sequence. Meanwhile, the data flow in the networks was divided into two directions: up and down with regard to the host. And the routing table in each station will be updated in accordance with the reporting information sent to the host. According to the characteristics of relay Ethernet, the routing table information will be simplified into two categories, namely uplink routing and downlink routing. And then, seismic data transmission software based on TCP could be programmed.4. The simulation for relay Ethernet was made based on NS2 simulation platform to study the factors which influence the data transmission rate in such topology. Three major factors were analyzed, namely point-to-point link speed, nodes forward speed, and the number of nodes. A method of synchronous uploading data for multiple stations was presented based on the feature of data transmission in seismic exploration.5. A seismic data acquisition system including hardware and software was designed and implemented based on the above relay Ethernet framework. The seismic data acquisition station and trigger station were designed based on 32-bit RISC ARM9 processor, 24-bit ADC, DAC, large-scale field programmable gate array (FPGA) and embedded Ethernet. The core control board was based on the AT91RM9200, which includes 64M memory, 16M Flash, and two 100M network interface. And the open source bootloader U-BOOT was ported and the board support package (BSP) for VxWorks was implemented. The data acquisition board and the trigger management board were designed based on 24-bit ADC and DAC, and the interface circuits were implemented in VHDL based on FPGA. The management software for distributed seismic data acquisition based on Windows XP and the embedded software station software based on VxWorks were also implemented.6. Instruments assembly and experiments were carried out. A 24-channel seismic instrument was made and was tested indoor. To resolve the power problem, a decentralized power supply model was established and the relationship between three main factors was studied: power supply voltage, power assumption of station and resistance of power line, which provided the basis for the design of seismic cable and power stations. And then field experiments with hammer source, pseudo random impact source and vehicle electromagnetic vibroseis - PHVS-10000 were carried out, and satisfactory results have been obtained.
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