Postseismic relaxation along the San Andreas fault at Parkfield from continuous seismological observations

Seismic velocity changes and nonvolcanic tremor activity in the Parkfield area in California reveal that large earthquakes induce long-term perturbations of crustal properties in the San Andreas fault zone. The 2003 San Simeon and 2004 Parkfield earthquakes both reduced seismic velocities that were measured from correlations of the ambient seismic noise and induced an increased nonvolcanic tremor activity along the San Andreas fault. After the Parkfield earthquake, velocity reduction and nonvolcanic tremor activity remained elevated for more than 3 years and decayed over time, similarly to afterslip derived from GPS (Global Positioning System) measurements. These observations suggest that the seismic velocity changes are related to co-seismic damage in the shallow layers and to deep co-seismic stress change and postseismic stress relaxation within the San Andreas fault zone.     

Nonvolcanic tremors deep beneath the San Andreas Fault

We have discovered nonvolcanic tremor activity (i.e., long-duration seismic signals with no clear P or S waves) within a transform plate boundary zone along the San Andreas Fault near Cholame, California, the inferred epicentral region of the 1857 Fort Tejon earthquake (moment magnitude approximately 7.8). The tremors occur between 20 to 40 kilometers' depth, below the seismogenic zone (the upper approximately 15 kilometers of Earth's crust where earthquakes occur), and their activity rates may correlate with variations in local earthquake activity.     

Tilt Precursors before Earthquakes on the San Andreas Fault, California

An array of 14 biaxial shallow-borehole tiltmeters (at 1O(-7) radian sensitivity) has been installed along 85 kilometers of the San Andreas fault during the past year. Earthquake-related changes in tilt have been simultaneously observed on up to four independent instruments. At earthquake distances greater than 10 earthquake source dimensions, there are few clear indications of tilt change. For the four instruments with the longest records (> 10 months), 26 earthquakes have occurred since July 1973 with at least one instrument closer than 10 source dimensions and 8 earthquakes with more than one instrument within that distance. Precursors in tilt direction have been observed before more than 10 earthquakes or groups of earthquakes, and no similar effect has yet been seen without the occurrence of an earthquake.     

Clustering and periodic recurrence of microearthquakes on the san andreas fault at parkfield, california

The San Andreas fault at Parkfield, California, apparently late in an interval between repeating magnitude 6 earthquakes, is yielding to tectonic loading partly by seismic slip concentrated in a relatively sparse distribution of small clusters (<20-meter radius) of microearthquakes. Within these clusters, which account for 63% of the earthquakes in a 1987-92 study interval, virtually identical small earthquakes occurred with a regularity that can be described by the statistical model used previously in forecasting large characteristic earthquakes. Sympathetic occurrence of microearthquakes in nearby clusters was observed within a range of about 200 meters at communication speeds of 10 to 100 centimeters per second. The rate of earthquake occurrence, particularly at depth, increased significantly during the study period, but the fraction of earthquakes that were cluster members decreased.     

A look inside the San Andreas Fault at Parkfield through vertical seismic profiling

The San Andreas Fault Observatory at Depth pilot hole is located on the southwestern side of the Parkfield San Andreas fault. This observatory includes a vertical seismic profiling (VSP) array. VSP seismograms from nearby microearthquakes contain signals between the P and S waves. These signals may be P and S waves scattered by the local geologic structure. The collected scattering points form planar surfaces that we interpret as the San Andreas fault and four other secondary faults. The scattering process includes conversions between P and S waves, the strengths of which suggest large contrasts in material properties, possibly indicating the presence of cracks or fluids.     

夏季草莓圣安德瑞斯无土栽培营养液配方筛选

为了筛选夏季草莓品种无土栽培的最佳营养液配比,以圣安德瑞斯品种作为材料,以霍格兰通用配方为对照,研究5种不同营养液配比对夏季草莓品种的生长性状、产量和品质的影响。结果表明,Ca(NO_3)_2·4H_2O,KNO_3,NH_4H_2PO_4,MgSO_4·7H_2O,NH_4NO_3含量分别为236,303,57,123,80 mg/L的营养液配比在株高、花序长、花枝数、花蕾数等方面优于其他处理。     

Earthquake Swarm Along the San Andreas Fault near Palmdale, Southern California, 1976 to 1977

Between November 1976 and November 1977 a swarm of small earthquakes (local magnitude 相似文献   

关于蓝莓植物学特性的研究

本文为了满足我国广大果农发展蓝莓之需要，详细介绍了关、日等国家对蓝莓植物学特性的研究情况，论述了蓝莓植物学特性与其种类、品种及栽培管理技术的相关性。     

烤烟对氯的吸收积累特性

采用大田试验。在基肥中用部分氯化钾替代硫酸钾,追肥仍然使用原专用追肥。研究在不同氯浓度处理下烤烟三个重要的生理时期(团棵期、现蕾期、成熟期)对氯的吸收积累特性,以及对氮、磷、钾吸收的影响。结果表明:对烤烟烟叶各部位氯含量的测定分析得出:烟叶氯的积累量为下部叶>中部叶>上部叶。团棵期烤烟氯的积累量随氯肥替代的增加出现曲折下降趋势,20%氯替代时达到最大积累量0.36%,现蕾期和成熟期各部烟叶在50%氯替代下,烟叶氯含量分别超过0.2%和0.5%。上部叶的烟叶含氮量随氯替代的增加而降低,中、下部叶含氮量无明显变化;各处理下,下部烟叶的钾含量均较上、中部烟叶高,无氯替代、20%氯替代和30%氯替代处理下差异较为明显,而上部烟叶与中部烟叶的含钾量无明显差异。施氯处理与不施氯处理对烟株磷含量的积累,无太大影响。     

"三农教育":解决"三农"问题的突破口

农业教育、农村教育和农民教育统称为“三农教育”,它与我国农民增收与就业、农业科技进步和农村经济发展等密切相关,也是解决“三农”问题的突破口;我国政府已经为解决农村和农民教育问题采取了许多重大举措,但是距“三农教育”问题的彻底解决路途还很遥远。     

Yoshizawa周期解定理的拓广

证明了有限时滞泛函数分方程解的一致最终有界性蕴含周期的存在性，从而推广了著名的Ｙｏｓｈｉｚａｗａ周期解定理。     

中药"三仙保健散"对肉仔鸡免疫功能的影响

选择健康1日龄Ross308肉仔鸡200只,随机分成4组,即A组（空白对照组）、B组（添加0.5%三仙保健散）、C组（添加1%三仙保健散）和D组（添加2%三仙保健散）,各组于7和28d用鸡新城疫疫苗滴鼻、点眼,于35日龄测定血液中NDV抗体水平,并检测＂三仙保健散＂对免疫器官和生长发育的影响。结果表明,＂三仙保健散＂能明显提高Ross308肉仔鸡免疫器官指数,提高NDV血凝抑制抗体效价,增强肉仔鸡机体免疫功能,促进肉仔鸡生长发育和降低死亡率。     

新台糖16号生产性能分析

新台糖16号系台湾糖业研究所选育而成.我区1994年引进试种观察,1996年参加广西甘蔗品种区域试验,本文根据区域试验结果对新台糖16号进行生产性能分析,以供参考.     

不同品种番石榴光合特性的研究

通过田间对3个番石榴品种光合特性的研究, 结果表明, 珍珠番石榴、水晶番石榴和土种番石榴叶片的光饱和点均为1 400μmol·m-2·s-1, 光补偿点分别为110 04、158 89和170 97μmol·m-2·s-1 光合表观量子产量(AQY)分别为0 011 5, 0 009和0 006 2 当PAR≥800μmol·m-2·s-1时, 珍珠番石榴叶片的Pn、Tr、Cs值最高, 水晶番石榴次之, 土种番石榴叶片的最低 随着PAR的增加, 3个品种番石榴叶片Ci呈逐渐下降趋势, 相同的光照强度下, 珍珠番石榴叶片Ci最低, 水晶番石榴次之, 土种番石榴叶片的Ci最大 珍珠番石榴年株产量显著高于水晶番石榴, 这与其具有较高的光合特性是相适应的     

“青皮散”乳液促实验动物胃肠动力的研究

[目的]考察＂青皮散＂乳液对胃轻瘫模型动物胃肠动力的影响,探讨其作用机制。[方法]建立胃肠动力障碍模型动物,测定灌服＂青皮散＂乳液后模型小鼠胃内容物残留率、小肠中阿拉伯胶活性炭粉混合物的推进距离;测定灌服＂青皮散＂乳液后模型大鼠血浆及胃、肠组织匀浆中胃动素（MTL）水平及其在胃窦和空肠中MTL的分布变化。[结果]＂青皮散＂乳液能明显加快胃肠动力障碍模型动物胃排空速率,降低胃内容物残留率,增加小肠推进百分比,显著升高胃肠动力障碍模型动物血浆及胃、肠组织匀浆中MTL水平,明显增加胃窦及空肠MTL阳性物质的表达。[结论]＂青皮散＂乳液促实验动物胃肠运动作用与血浆、胃、肠组织匀浆MTL水平的增加及胃肠道MTL细胞分布变化有关。