内蒙古中西部地区震源参数和场地响应反演

采用Atkinson方法，基于遗传算法，利用呼和浩特数字地震台网7个子台记录的9次质量较高的地震事件资料，计算了内蒙古中西部地区的品质因子Q值和非弹性衰减系数c（f）。在所研究的频率范围内，前者和频率．厂有很好的线形关系：Q（f）=116．8f^1.000后者与频率．厂的变化关系不明显。在此基础上采用Moya方法反演了7个地震台的场地响应和地震的震源参数，并对它们之间的相互关系进行了讨论。结果显示在所研究的频率域内7个基岩台站的场地均不同程度的存在放大作用，其次震源参数间具有较好的线性关系。本文还详细介绍了Atkinson方法和Moya方法的原理和计算步骤。     

Understanding the Past and Present and Predicting the Future: Farmers’ Use of Multiple Nutrient Best Management Practices in the Upper Midwest

Understanding what drives farmers’ voluntary adoption of nutrient and soil best management practices has important consequences for many environmental outcomes including water quality. We build on research revealing the need for simultaneous use of multiple nitrogen best management practices to achieve water quality improvement goals. Using social, economic and attitudinal variables we predict the use of multiple nitrogen best management practices at three time points: current use (2013), past use (before 2013), and likelihood of use on their largest field in the next three years. Our empirical analysis uses structural equation modeling with latent variables and 2014 farmer survey data from three Midwestern US states. Most farmers in our sample used at least one of the six best management practices. Our results reveal that farmers’ attitudes, use of information sources, and conservation program participation affect the number of nitrogen best management practices concurrently in use at multiple time points.     

中西部地区承接产业转移的影响因素研究

将中西部地区划分为东北、中部、西北、西南4个区域,采用1995—2013年的相关数据,分析各区域在承接东部发达地区产业转移过程中的主要影响因素。选取的影响因素包括资本存量、经济规模、劳动力成本、人力资源和路径效应。结果发现:4个区域的路径效应、资本存量与产业转移承接地均存在显著正相关关系;人力资源与产业转移承接地存在正相关关系,但东北、西北地区不显著;劳动力成本与产业转移承接地存在负相关关系,但对东北地区不显著;除中部地区外,经济规模与产业转移承接地并不存在显著相关关系。中西部区域地方政府和企业家在促进产业转移进程中应充分发挥比较优势,根据不同影响要素制定宏观政策与微观引资策略。     

Integrating Stalagmite, Vertebrate, and Pollen Sequences to Investigate Holocene Vegetation and Climate Change in the Southern Midwestern United States

Speleothem carbon and oxygen isotopic records from Onondaga Cave, south-central Missouri, and Beckham Creek Cave, north-central Arkansas, are compared with the Cupola Pond and Oldfield Swamp pollen series from southeastern Missouri and the Rodgers Shelter and Modoc Shelter vertebrate biostratigraphic sequences from central Missouri and southwestern Illinois. Similar, and roughly contemporaneous, shifts between deciduous forest and steppe indicators throughout the Holocene are revealed in each database. These independent proxies record steppe conditions between approximately 9000 and 1500 cal yr B.P. A shift toward lighter speleothem carbon may reflect a change from warm and dry to cool and dry conditions between 4500 and 3000 yr B.P. The sensitive response of speleothem δ¹³C to changes in vegetation emphasizes their importance as paleoclimate records in an area containing few other millenial-scale climate proxies.     

The Emergence of Standardized,Idealized, and Placeless Landscapes in Midwestern Main Street Postcards

Although Main Streets line small towns from Florida to Alaska, Main Street is more than just a street name; it is a place imbued with local pride, regional identity, and national virtues. This symbolic connection derives from the Midwestern Main Streets of the first half of the twentieth century, a time that coincides with the golden age of the picture postcard. This article explores how the connotative and denotative symbols from this golden age overlap. A sample of 140 postcards from small towns in Kansas and Nebraska with a viable Main Street from 1900 to 1945 was selected from books, personal collections, and Internet auction sites. Our discovery of a disconnect between picture postcard and reality was not surprising, but there was a shift from the significance of basic denotative signs and the particularities of individual Main Streets in the early part of the twentieth century to an increased importance of connotative signs unifying a homogeneous Main Street ideal. Three distinct eras of postcard manipulation emerged from the data: A slightly manipulated 1900–1911 era, a 1912–1930 era emphasizing a corridor of progress, and a 1931–1945 era that displayed a growing detachment from reality and moved from the unique characteristics of a particular town toward a homogenized and idealized “Main Street view.” This article offers empirical evidence for the theoretical propositions of humanist and critical geographers that the representations of the American landscape are becoming increasingly homogenized, contrived, and placeless.     

Nature,Affordability, and Privacy as Motivations for Exurban Living

Current demographic trends indicate that the 21st century will be one of exurban growth as more Americans seek out countryside home sites and their accompanying lifestyles. Two of the literature's conventional wisdoms regarding exurban migration motivations are critically examined in this study: (1) exurbanites are seeking home sites in close proximity to natural places, and (2) exurbanites are drawn to countryside areas because of the affordability of such locations. This study uses 34 snowball-sampled, semistructured interviews from Indiana and Illinois exurbanites to examine these two commonly held beliefs. Subjects reported that the natural environment did not primarily motivate their moves. Current home sites were, however, attractive due to their perceived affordability. The main, and remarkable, finding of this study is the strong desire for privacy that drew people to exurbia. The desire for privacy was cited as a main motivator by a large majority of the subjects interviewed.     

INTRINSIC THRESHOLDS IN SOIL SYSTEMS

The threshold concept has been applied with considerable success to the understanding of geomorphic systems. Both intrinsic and extrinsic thresholds can be recognized in soil systems, but intrinsic thresholds have previously been largely ignored. Examples of intrinsic thresholds in soils include minimum levels of sesquioxides for immobilization of organic matter in spodic horizons, leaching of carbonates before clay movement can take place, and certain minimum clay mineral ratios before a pedogenic regime dominated by pedoturbation can occur. Recognition of intrinsic thresholds explains soil instability in the absence of environmental change.     

INFORMATION SOURCES FOR NINETEENTH CENTURY MIDWESTERN MIGRATION*

A variety of sources provides different levels of information about the origins of nineteenth century migrants to the Midwest. The advantages and disadvantages of four of the most common records, the federal census, land office records, genealogical collections, and county histories/biographies/atlases, are examined. Characteristics considered are the specific types of data provided, extent of coverage, level of detail, statistical reliability, and accessibility. Examples of studies using each record type are cited.     

内蒙古中西部地区尾波Q值研究

基于Sato单次散射模型,利用2001-2006年6月内蒙古数字地震台网记录到的发生在内蒙古中西部地区的114条ML≥2.7地震波形资料,从西到东分三个研究区对内蒙古中西部地区尾波Q值进行了研究,研究中首先计算各条记录尾波4~18 Hz间15个频率点的尾波Q值,并对Q值与频率之间的依赖关系进行了拟合,拟合结果为:Ⅰ区Qc(f)=(69.98±20.92)f(0.8989±0.0881);Ⅱ区Qc(f)=(55.59±14.726)f(0.9426±0.1084);Ⅲ区Qc(f)=(69.89±18.54)f(0.8352±0.0913)。研究结果表明,尾波值表现出明显的分区性特征,研究区Ⅰ、Ⅲ表现为高Q值,研究区Ⅱ为低Q值,其结果可能与内蒙古中西部地区独特的构造分区特征有关。     

Deglaciation, basin formation and post-glacial climate change from a regional network of sediment core sites in Ohio and eastern Indiana

Many paleoclimate and landscape change studies in the American Midwest have focused on the Late Glacial and early Holocene time periods (~ 16–11 ka), but little work has addressed landscape change in this area between the Last Glacial Maximum and the Late Glacial (~ 22–16 ka). Sediment cores were collected from 29 new lake and bog sites in Ohio and Indiana to address this gap. The basal radiocarbon dates from these cores show that initial ice retreat from the maximal last-glacial ice extent occurred by 22 ka, and numerous sites that are ~ 100 km inside this limit were exposed by 18.9 ka. Post-glacial environmental changes were identified as stratigraphic or biologic changes in select cores. The strongest signal occurs between 18.5 and 14.6 ka. These Midwestern events correspond with evidence to the northeast, suggesting that initial deglaciation of the ice sheet, and ensuing environmental changes, were episodic and rapid. Significantly, these changes predate the onset of the Bølling postglacial warming (14.8 ka) as recorded by the Greenland ice cores. Thus, deglaciation and landscape change around the southern margins of the Laurentide Ice Sheet happened ~ 7 ka before postglacial changes were felt in central Greenland.