| Earth crust is in a state of continuous motion which releases various informationof tectonic movement covering a wide range in both frequency band and energy. Inmost of current observations to such movement, the frequency is lower than100Hz,while little involves in ultrahigh-frequency signals (higher than1kHz). Earthquakesare a form of sudden crustal movement, or a kind of ultrahigh-frequency tectonicactivity. A major earthquake is a process from tiny rupturing, to gradual spread, finallyto avalanche and failure of a fault. The seismogenic zone is a three-dimensionaldeformation volume containing the surface fault and rock in the subsurface, thus theassociated tectonic activity should manifest itself over a distance of several kilometersin shallow crust. Because there are a great number of seismically active areas in vastChina, it is impossible to deploy dense seismic stations all around the country.Therefore it is required to develop a multi-parameter telemeter for observing tectonicactivity with ultrahigh frequency, miniaturization and wireless telemetry, so as tocollect signals from observation points set at the important tectonic positionsstructural geologists expected and to improve the study of micro tectonic activityand efforts of earthquake prediction.This thesis presents an ultrahigh-frequency tectonic activity telemeter ofindependent research and development. The maximum sampling frequency of thetelemeter is100kHz and the sampling rate of it is18bit. There are3signal channelsconnecting the ultrahigh frequency seismic sensor and electromagnetic field signalsensor. The telemeter is encapsulated in a waterproof stainless steel tube withdiameter of about50mm and height of about400mm, which is suitable for installationin shallow strata（0-200m）of the earth. The observational data can be uploaded realtime to a remote sensing center by wireless networks. The development of ultrahigh-frequency telemeter for observing near field tectonic activity can provide a suitabletool for field survey of active tectonics and a new approach to improve the temporaland spatial resolution of earthquake monitoring.This thesis also describes the tests of this instrument on a vibrator vehicle in Yanjiao, Hebei Province, and on an artificial hypocenter in the Huangyang beach,Xuanhua County, and the continuous observations to earthquake signals in Dali,Yunnan Province. The results of the tests on the vibrator vehicle prove that theultrahigh-frequency seismic telemeter is able to accurately respond to high-frequencyseismic activity with frequency higher than100Hz. Then the attenuation law in sandwas gained by analyzing the testing results of the artificial hypocenter. In thecontinuous seismicity observations in Dali, the corresponding earthquake locating andspectral analysis were conducted. It was proved that high frequency microearthquakescaused by crustal movement do exist and can be recorded by the telemeter. Therecorded microearthquakes are of magnitudes between Mw=-3.0and Mw=-1.0, withmaximum hypocentral distance up to4.87km, dominant frequency ranging from100Hz to300Hz, and maximum frequency as high as800Hz. It is possible that theultrahigh-frequency microseismicity observation (UFMO) will become a newapproach to the study on tectonic movement in small regions. |
