Sedimentary environment and development controls of the hydrocarbon source beds:Middle and Upper Proterozoic in northern North China

Problem on development control of marine source bed hold in Chinese petroleum industry progression. The Hongshuizhuang Formation,Tieling Formation and Xiamaling Formation in the Middle and Upper Proterozoic are important hydrocarbon source beds in northern North China, and investigation of their sedimentary environments and the controls has great significance for petroleum exploration in North China. Based on sedimentology (sequence stratigraphy), palaeoecology, sedimentary geochemistry, and sedimentary palaeogeography, their development pattern is discussed. All these studies indicate that the development controls of the hydrocarbon source beds include a favorite palaeogeographic location, exceeding propagation of biomes in low and middle latitudes, anoxic environments, enrichment of phosphorus element and the adsorption of clay minerals during the preservation of organic matter in the marine carbonates.     

Similarities between strike-slip faults at different scales and a simple age determining method for active faults

Abstract Several differently scaled strike‐slip faults were examined. The faults shared many geometric features, such as secondary fractures and linkage structures (damage zones). Differences in fault style were not related to specific scale ranges. However, it was recognized that differences in style may occur in different tectonic settings (e.g. dilational/contractional relays or wall/linkage/tip zones), different locations along the master fault or different fault evolution stages. Fractal dimensions were compared for two faults (Gozo and San Andreas), which supports the idea of self‐similarity. Fractal dimensions for traces of faults and fractures of damage zones were higher (D ～1.35) than for the main fault traces (D ～1.005) because of increased complexity due to secondary faults and fractures. Based on the statistical analysis of another fault evolution study, single event movements in earthquake faults typically have a maximum earthquake slip : rupture length ratio of approximately 10^?4, although this has only been established for large earthquake faults because of limited data. Most geological faults have a much higher maximum cumulative displacement : fault length ratio; that is, approximately 10^?2 to 10^?1 (e.g. Gozo, ～10^?2; San Andreas, ～10^?1). The final cumulative displacement on a fault is produced by accumulation of slip along ruptures. Hence, using the available information from earthquake faults, such as earthquake slip, recurrence interval, maximum cumulative displacement and fault length, the approximate age of active faults can be estimated. The lower limit of estimated active fault age is expressed with maximum cumulative displacement, earthquake slip and recurrence interval as T ? (d_max /u) · I(M).     

Change of crustal gravitational potential energy in the Taiwan orogen by the Chi-Chi earthquake sequence

The active convergence between the northwest corner of the Philippine Sea Plate and the southeast margin of the Eurasian Plate has given rise to the Taiwan mountain-building and produced numerous earthquakes. Among the earthquakes, the 1999 Chi-Chi earthquake is the largest one recorded in the century. In this study, we examine the crustal gravitational potential energy (GPE) change in the Taiwan orogen caused by the Chi-Chi earthquake sequence, which was catalogued by the regional broadband seismometer array for a whole year. As a result, we find that the crust was going up and down randomly during the earthquake sequence, but an overall cumulative gain of the crustal GPE, +1.82×10¹⁶ J, was rapidly achieved in 1 month after the main shock. The crustal GPE was nearly still afterwards and reached +1.90×10¹⁶ J in 1 year. Spatially, although the main surface faulting has occurred in western Taiwan, the crustal GPE gain is mainly distributed in central Taiwan at the area where the existing crustal GPE is high and the existing lithospheric GPE is relatively low. The crustal GPE loss by the Chi-Chi earthquake sequence can also be observed and is generally distributed at both sides of the crustal GPE gain area. The crustal GPE gain mainly found in central Taiwan corroborates that the uplift of the Taiwan orogen is principally taking place in central Taiwan, rather than in the more hazardous western Taiwan.     

Earthquake‐related geomorphic environment and pond sediment information

Shaking during the 1995 Kobe earthquake caused surface material to be more mobile in catchment areas in the Rokko Mountains, Kobe, where there are some active fault lines. As a result, there were many landslides associated with the earthquake. The sedimentation rate in a pond in the mountains increased several fold, then exponentially decreased with seasonality over several years. Six years after the earthquake there were no marked surface movements related to the earthquake, even though the sedimentation rates had increased slightly. A new steady state for the structure of the earthquake‐modi?ed surface had evidently been reached. Copyright © 2004 John Wiley & Sons, Ltd.     

Earthquake relocation and 3-dimensional crustal structure of P-wave velocity in cen-tral-western China

IntroductionUnderstandingthemechanismofcontinentalearthquakesisveryimportantforseismichaz-ardpreventionandearthquakeprediction.Themodernseismotectonictheoryandtheideaofearthquakepredictionaredevelopedmainlyfromthestudiesoninterplateearthquakes,whicharedifficulttoexplainthephenomenaofintraplateearthquakes,suchasthecontinentalearthquakesoccurredinChinesemainland.Whiletheinterplateearthquakesoccurredalongtheplatebounda-ries,theintraplateearthquakesdistributediffuselyintheinterioroftheplates.Thus…     

Large aftershocks triggering by Coulomb failure stress following the 2001 M_S=8.1 great Kunlun earthquake

IntroductionItisshowedbyresearchesonearthquakestresstriggeringrecentlythatsmall'static'stresschangesduetopermanentfaultdisplacementcanalterthelikelihoodof,ortrigger,earthquakesonnearbyfaults(Harris,1998).Manystudiesoftriggeringinthenear-field,particularlyofaftershocks,showthesestaticchangesaretriggeringagent(Kilb,etal,2000).ReasenbergandSimpson(1992)studiedthere-sponseofregionalseismicitytothestaticstresschangeproducedbyLomaPrietaearthquake,andtheresultsshowedthataftershockratesincreasedinre…     

Probability-consistent spectrum and code spectrum

IntroductionInChina,thecombinationofseismicdesigncodewithzoningmapofseismicintensityorgroundmotionparametersisusuallyadoptedtodeterminetheseismicfortificationcriterionforthegeneralindustryandcivilbuildings.Thepresentproceduresareasfollows.Accordingtothepro-jectlocation,thedesignbasicaccelerationofgroundmotionandthedesigncharacteristicperiodofresponsespectrumareobtainedfromthezoningmapofseismicgroundmotionparameters(GeneralAdministrationofQualitySupervision,InspectionandQuarantineofthePeople…     

3-D rheologic model of earthquake preparation (II): Strain field and its applications

Introduction Based on the elastic theory of the hard inclusion (Dobrovolskii, 1991), we developed an inclusion theory of rheologic medium, and applied the results of bulk-strain field of a rheologic inclusion model to explain the spatial-temporal evolution process of earthquake precursors (SONG, et al, 2000). In the former paper (SONG, et al, 2003), we derived the viscoelastic displacement field of the rheologic inclusion model on the basis of the analytic expression of displacement field o…     

Investigation of upper crust anisotropy in Ghaen-Birjand region, east-central Iran

IntroductionWhenpropagatingthroughananisotropicmedium,ashearwavesplitsintotwo(quasi)shearwaveswithdifferentpropagationspeedsandpolarizedorthogonally.Owingtotherecentdevel-opmentofseismicobservationsystem,detectionofshearwavessplittingwithverysmalldelaytimesbetweenfasterandslowershearwavesbecameavailableandprovidedpowerfulapproachfordetectionofcrustalanisotropy.Crampin(1978)emphasizedtheroleofalignedmicrocracksasacauseofcrustalanisotropyandpointedoutthatforverticallyalignedmicrocracksthedirecti…     

3-D finite element modeling for evolution of stress field and interaction among strong earthquakes in Sichuan-Yunnan region

Introduction Sichuan-Yunnan region is a major area with frequent strong earthquakes in Chinese mainland, especially the middle-southern segment of South-North Seismic Zone, where many strong earth-quakes occurred in history. In the past 30 years, Sichuan-Yunnan region has two seismically active periods: one is from Tonghai earthquake in 1970 to Longling-Songpan earthquake in 1976, the other is from Lancang earthquake in 1988 to now. During this two periods, the M=7.7 Tonghai, M=7.1 Dagua…