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At least 235 records · Page 13Linked to original sources
USGS2023

Flood-frequency analysis in the Midwest: Addressing potential nonstationarity of annual peak-flow records

Flood-frequency analysis is essential in numerous water-resource management applications, including critical structure design and flood-plain mapping. A basic assumption within Bulletin 17C [1], the standardized guidelines for conducting flood-frequency analysis, is that basins without major hydrologic alterations, such as regulation or urbanization, exhibit stationary statistical properties of the distribution of annual peak streamflow. That is, the mean, variance, and skew are constant over time and the peak-flow record is a representative sample of the population of future floods [1]. In recent decades, better understanding of long-term climatic persistence and concerns about climate and land-use change have caused the assumption of stationarity in peak-flow records to be reexamined [2, 3, 4, 5]. Under nonstationary conditions, the long-term distributional properties (mean, variance, and/or skew) of peak-flow series change one or more times, either gradually or abruptly. Nonstationarities may be attributed to one source, but are often a result of a mixture of drivers, making detection and attribution of nonstationarities challenging [6, 7, 8]. Failure to incorporate observed trends and abrupt changes into flood-frequency analysis may result in a poor representation of the true flood risk. Bulletin 17C currently offers no guidance on how to account for nonstationarities when estimating floods and acknowledges the benefit additional flood frequency studies that incorporate changing climate or basin characteristics into the analysis would provide[1].

Midwest↗
USGS1972

Catalog of earthquakes along the San Andreas fault system in central California for the year 1971

A network of seismograph stations was established by the National Center for Earthquake Research (NCER) to study in detail the earthquakes along the San Andreas fault system in central California (Eaton, Lee, and Pakiser, 1970). This report, in the form of a catalog, summarizes the results of routine earthquake locations from that network for the year 1971, and provides the basic data for further studies to be published elsewhere. Similar catalogs for 1969 and 1970 have been prepared by Lee, Roller, Bauer, and Johnson, (1972), and Lee, Roller, Meagher, and Bennett, (1972). We located a total of 2,429 events that occurred in 1971 from primarily 34,111 first P-wave arrival times recorded at 121 seismograph stations. Among these events, 339 were blasts (mostly in quarries), 8 were suspected blasts, and 41 were either too far away from available stations or too small in magnitude to be adequately located. The remaining 2,041 events which were identified as earthquakes are presented in the catalog. The 121 seismograph stations consisted of 93 telemetered stations operated by NCER, and 28 stations operated by several other organizations. Readings from the latter stations were obtained through the courtesy of the Seismographic Stations, University of California, Berkeley, the Earthquake Mechanism Laboratory, National Oceanic and Atmospheric Administration, San Francisco, and the California Department of Water Resources, Sacramento. Data on local earthquakes in northern California, Nevada, and Oregon have been published in the Bulletins of the Seismographic Stations of the University of California, Berkeley (UCB) for many decades. The present catalog covers earthquakes which occurred in a smaller area but in greater detail than those covered by the UCB Bulletins. For example, the UCB Bulletins for 1971 (Cloud and Qamar, 1972; Cloud, Tomblin, and Litehiser, 1972) list a total of 116 earthquakes (most with magnitude greater than 2.5) in the region covered by this report (a coastal strip from Santa Rosa to Parkfield). In addition, we attempted to use all available data in locating earthquakes within and near our seismic network.

California↗
USGS1973

Catalog of earthquakes along the San Andreas fault system in Central California, April-June 1972

Numerous small earthquakes occur each day in the coast ranges of Central California. The detailed study of these earthquakes provides a tool for gaining insight into the tectonic and physical processes responsible for the generation of damaging earthquakes. This catalog contains the fundamental parameters for earthquakes located within and adjacent to the seismograph network operated by the National Center for Earthquake Research (NCER), U.S. Geological Survey, during the period April - June, 1972. The motivation for these detailed studies has been described by Pakiser and others (1969) and by Eaton and others (1970). Similar catalogs of earthquakes for the years 1969, 1970 and 1971 have been prepared by Lee and others (1972 b, c, d). A catalog for the first quarter of 1972 has been prepared by Wesson and others (1972). The basic data contained in these catalogs provide a foundation for further studies. This catalog contains data on 910 earthquakes in Central California. A substantial portion of the earthquakes reported in this catalog represents a continuation of the sequence of earthquakes in the Bear Valley area which began in February, 1972 (Wesson and others, 1972). Arrival times at 126 seismograph stations were used to locate the earthquakes listed in this catalog. Of these, 101 are telemetered stations operated by NCER. Readings from the remaining 25 stations were obtained through the courtesy of the Seismographic Stations, University of California, Berkeley (UCB); the Earthquake Mechanism Laboratory, National Oceanic and Atmospheric Administration, San Francisco (EML); and the California Department of Water Resources, Sacramento. The Seismographic Stations of the University of California, Berkeley, have for many years published a bulletin describing earthquakes in Northern California and the surrounding area, and readings at UCB Stations from more distant events. The purpose of the present catalog is not to replace the UCB Bulletin, but rather to supplement it, by describing the seismicity of a portion of central California in much greater detail.

California↗
USGS1976

Catalog of earthquakes along the San Andreas fault system in central California, July-September 1973

Numerous small earthquakes occur each day in the Coast Ranges of central California. The detailed study of these earthquakes provides a tool for gaining insight into the tectonic and physical processes responsible for the generation of damaging earthquakes. This catalog contains the fundamental parameters for earthquakes located within and adjacent to the seismograph network operated by the National Center for Earthquake Research (NCER), U. S. Geological Survey, during the period July-Sptember, 1973. The motivation for these detailed studies has been described by Pakiser and others (1969) and by Eaton and others (1970). Similar catalogs of earthquakes for the years 1969, 1970, and 1971 have been prepared by Lee and others (1972b, c, and d). Catalogs for the first, second, third, and fourth quarters of 1972 and the first and second quarters of 1973 have been prepared by Wesson and others (1972a, b, 1973b, and 1974a and b), and by Bufe and others (1975). The basic data contained in these catalogs provide a foundation for further studies. This catalog contains data on 949 earthquakes in central California. Arrival times at 132 seismograph stations were used to locate the earthquakes listed in this catalog. Of these 117 were telemetered stations operated by NCER. Readings from the remaining 15 stations were obtained through the courtesy of the Seismographic Stations, University of California, Berkeley (UCB), and the California Department of Water Resources, Sacramento. The Seismographic Stations of the University of California, Berkeley, have for many years published a bulletin describing earthquakes in northern California and the surrounding area and listing readings at UCB Stations from more distant events. The purpose of the present catalog-is not to replace the UCB Bulletin, but rather to supplement it, by describing the seismicity of a portion of central California in much greater detail.

California↗