1605年武昌地震考

1605年湖北武昌府发生破坏性地震,由于历史资料的缺乏,地震的震级、震中位置未作确切的评定。本次工作主要是根据历史资料和武汉市地震地质背景对1605年地震的参数和构造作进一步评述。

地震史料《云南地震考》的科学价值研究

1926年童振藻所著的《云南地震考》是云南历史上首部关于地震研究的专著,书中对云南地震的成因、震史、震灾预防等都进行了详细阐述,尤其在云南地震成因、地震诱因、地震区域划分等方面的观点,对当时的地震研究工作来说,都具有标志性意义,是云南地震研究者的重要参考资料。文章从《云南地震考》一书中提取了对地震科学研究的价值,并对该书的科学意义和历史地位作了肯定性探讨。

Reconstruction of Mechanical Principles of Zhang Heng's Seismoscope

The difficulties in the reconstruction of Zhang Heng’s Seismoscope come mainly from the lack of understanding of its mechanical principles. Such a discrepancy affects the rational reconstruction of the external form of the seismoscope and the fair assessment of its position in science. In connection with the two basic conjectures on its basic principles over the past hundred years: namely, the suspended pendulum and the upright rod, the authors have conducted a comprehensive study from the viewpoint of modern seismology. In this study, various aspects are involved, such as the properties of the seismoscope, its description in the “History of the Latter Han Dynasty", the structure and movement of the central pillar, historical earthquakes in the Longxi region, earthquake intensity in Luoyang, and modern seismograms from the Luoyang seismic station. The result shows that Zhang Heng’s seismoscope works following a suspended pendulum principle; it is triggered to move by seismic Rayleigh waves; and resonance plays the role of amplification. The long-prevailing conjecture of the upright rod, which was mistakenly called the “inverted pendulum" for a time, is believed to be improper. Both theory and practice show that it cannot be used in a seismoscope and will lead to an irrational reconstruction of the external form.

Zhang Heng's Seismoscope( 2):Historical Materials and Investigation

Historical data regarding Zhang Heng's seismoscope is not singular proof. Actually,the four earliest historical documents,i. e.,Continuation of Historiography of Han Dynasty, Historiography of the Later Han,Book of the Later Han and Ding Record all have relevant records of its structure,size,principle,response to earthquake and actual applications. These five aspects are supported by archaeological research,unearthed cultural relics, historical earthquakes and modern seismological study. These historical materials contain a great deal of specific information about this ancient seismoscope. In conclusion, the authenticity and reliability of Zhang Heng's seismoscope are verified.

Deep Seismic Exploration in the Taiwan Straits: The HX9 Survey Line Experiment and Preliminary Results

By using an offshore large volume air-gun seismic source, onshore seismic stations( including mobile stations and permanent stations) and ocean bottom seismometers,a deep seismic exploration experiment was carried out for the first time in the Taiwan Straits. Results show that seismic stations can receive seismic signals from the air-gun arrays of the "YANPING Ⅱ"scientific investigation ship from as far as 280 km away.Tens of thousands of high quality seismic data items were obtained successfully and different types of P-wave seismic phases were identified. A one-dimensional crustal structure model of the survey profile HX9 shows that the crustal structure,which is reflected by Pc and Pm P reflection waves from two velocity discontinuities and basement refraction wave( Pg) constitutes the basic characteristic of the crustal structure in this region. The depths of Conrad discontinuity and Moho discontinuity are respectively16. 0km- 17. 5km and 28. 0km- 29. 5km.

The Emergency Scientific Investigation on the Surface Rupture Zone of the M_S 7.1 Yushu Earthquake

The coseismic surface rupture zone of the seismogenic fault of the Ms7.1 Yushu earthquake includes three left-stepping main ruptures, striking 300°- 320°, in general. An approximately 2km-long en echelon tension fissure zone was found at Longbao town. The main rupture in the northern part is about 16km long, about 9kin long in the middle part, and about 7km long in the southern part, with a total length of 34km. Each of the main ruptures consists of a series of en echelon sub-ruptures represented by a series of compression bulges alternating with tension fissures or by en echelon fissures. The rupture at Changusi, the southernmost of the ruptures, is characterized by vertical displacement, with a value of 50cm. The rupture zone shows left-lateral strike-slip characteristics. The maximal horizontal slip is on the northern main rupture, with a value of 1.8m.

Lithospheric structure and faulting characteristics of the Helan Mountains and Yinchuan Basin： Results of deep seismic reflection profiling

The Helan Mountains and Yinchuan Basin （HM-YB） are located at the northern end of the North-South tectonic belt, and form an intraplate tectonic deformation zone in the western margin of the North China Craton （NCC）. The HM-YB has a complicated history of formation and evolution, and is tectonically active at the present day. It has played a dominant role in the complex geological structure and modem earthquake activities of the region. A 135-km-long deep seismic reflection profile across the HM-YB was acquired in early 2014, which provides detailed information of the lithospheric structure and faulting characteristics from near-surface to various depths in the region. The results show that the Moho gradually deepens from east to west in the depth range of 40-48 km along the profile. Significant differences are present in the crustal structure of different tectonic units, including in the distribution of seismic velocities, depths of intra-cmstal discontinuities and undulation pattern of the Moho. The deep seismic reflection profile further reveals distinct structural characteristics on the opposite sides of the Helan Mountains. To the east, The Yellow River fault, the eastern piedmont fault of the Helan Mountains, as well as multiple buried faults within the Yinchuan Basin are all normal faults and still active since the Quaternary. These faults have controlled the Cenozoic sedimentation of the basin, and display a ＂negative-flower＂ structure in the profile. To the west, the Bayanhaote fault and the western piedmont fault of the Helan Mountains are east-dipping thrust faults, which caused folding, thrusting, and structural deformation in the Mesozoic stratum of the Helan Mountains uplift zone. A deep-penetrating fault is identified in the western side of the Yinchuan Basin. It has a steep inclination cutting through the middle-lower crust and the Moho, and may be connected to the two groups of faults in the upper crest. This set of deep and shallow fault system consists of both strike-slip, thrust, and normal faults formed over different eras, and provides the key tectonic conditions for the basin-mountains coupling, crustal deformation and crust-mantle interactions in the region. The other important phenomenon revealed from the results of deep seismic reflection profiling is the presence of a strong upper mantle reflection （UMR） at a depth of 82-92 km beneath the HM-YB, indicating the existence of a rapid velocity variation or a velocity discontinuity in that depth range. This is possibly a sign of vertical structural inhomogeneity in the upper mantle of the region. The seismic results presented here provide new clues and observational bases for further study of the deep structure, structural differences among various blocks and the tectonic relationship between deep and shallow processes in the western NCC.

Submarine slide evidence for late Miocene strike-slip reversal of the Red River Fault

During the late Miocene(~5.5 Ma), a large-scale submarine slide with an area of approximately 18000 km^2 and a maximum thickness of 930 m formed in the deep-water region of the Qiongdongnan Basin. The large-scale submarine slide has obvious features in seismic profile, with normal faults in the proximal region, escarpments at the lateral boundary, and a pronounced shear surface at the base. The internal seismic reflections are chaotic and enclosed by parallel and sub-parallel seismic events.The main direction of sediment transport was from south to north and the main sediment source was the southern region of the Qiongdongnan Basin, which is located in the east of the Indo-China Peninsula and the north of the Guangle uplift. In this region,late Miocene strike-slip reversal of the Red River Fault, uplift and increased erosion of the Indo-China Peninsula, and an abrupt rise in the rate of deposition in the western part of the South China Sea provided the basic conditions and triggering mechanism for the large-scale submarine slide. The discovery of the large-scale submarine slide provides sedimentological evidence for the tectonic event of late Miocene strike-slip reversal of the Red River Fault. It can also be inferred that the greatest tectonic activity during the process of the Red River Fault reversal occurred at ~5.5 Ma from the age of top surface of the submarine slide.

New imaging method for seismic reflection wave and its theoretical basis

Some new imaging formulas for seismic reflection wave and theirtheoretical basis are given. Phenomena of wave propagation should be characterized by instantaneous spectrum and expressed by complex function of three variables (time, space and frequency) in mathematics. Various physical parameters of medium are also complex functions of two variables (space and frequency). The relationship between reflection coefficient of medium and spectrum of reflected wave is given. Multi-reflection and filter of formations are considered in inversion formulas. Prob-lems in classical convolution model and wave equation are illustrated. All these inversion formulas can be used to image underground medium by wavelet transform and method of '3-basic colors'. Different colors mean different media.