Estimation on site-amplification from different methods using strong motion data obtained in Tangshan, China

Introduction It has been known that each soil type responds differently when it is subjected to ground mo-tion from earthquakes. So, the study of local site effects on seismic ground motions is one of the most important goals of earthquake engineering. It is practical importance to develop methods for assessing the nature and potential of sediment amplification, especially when choosing the location and design of critical and essential facilities. At present, however, the method by which site …     

Comparative dating of a Bison-bearing late-Pleistocene deposit,Térapa,Sonora, Mexico

A recently discovered Bison-bearing fossil locality at Térapa, Sonora, Mexico, had previously been dated to 440 ± 130 ka using whole rock ⁴⁰Ar/³⁹Ar on a basalt flow that impounds the deposit. This age is considerably older than the accepted age of about 240–160 ka for the migration of Bison into greater North America. The Térapa deposit also contains a mixture of fossils from extralimital or extinct tropical animals and temperate animals. Constraining the age of the deposit is critical to interpret the paleontologic and paleoclimatologic implications of this unique Sonoran fossil locality. Three additional geochronological methods have been applied to this deposit (infrared stimulated luminescence (IRSL), amino acid racemization (AAR), and radiocarbon) and the data from the original ⁴⁰Ar/³⁹Ar age were revisited. The IRSL data suggest that the impounding basalt flow and the sediments that abut it were emplaced 43 ka ago and that the oldest sediments were deposited shortly after. Two radiocarbon ages suggest the fossiliferous sediments were emplaced by 42 ka. Effective diagenetic temperatures inferred from the AAR results, combined with AAR data from a similar-age deposit in southern Arizona, are in accordance with the 40–43 ka age estimates. For the AAR results to corroborate the ⁴⁰Ar/³⁹Ar age, the effective diagenetic temperature for the area would need to be approximately 3 °C, which is unrealistically low for northern Mexico. The new geochronological results suggest the Térapa deposit and fossils are 40–43 ka old. The anomalously old ⁴⁰Ar/³⁹Ar age for the impounding basalt is probably the result of low ⁴⁰Ar* concentrations and inherited ⁴⁰Ar.     

Spatio-temporal analysis and derivation of copula-based intensity–area–frequency curves for droughts in western Rajasthan (India)

This study presents spatio-temporal analysis of droughts in one of the most drought prone region in India–western Rajasthan and develops drought intensity-area-frequency curves for the region. The meteorological drought conditions are analyzed using 6-month standardized precipitation index (SPI-6) estimated at spatial resolution of 0.5° × 0.5°. Spatio-temporal analysis of SPI-6 indicates increase in frequency of droughts at the central part of the region. The non-parametric Mann–Kendall test for seasonal trend analysis showed increase in number of grids under drought during the study period. Further, bivariate frequency analysis of drought characteristics—intensity and areal extent is carried out using copula methods. For modeling joint dependence between drought variables, three copula families namely Gumbel-Hougaard, Frank and Plackett copulas are evaluated. Based on goodness-of-fit as well as upper tail dependence tests, it is found that the Gumbel-Hougaard copula best represents the drought properties. The copula-based joint distribution is used to compute conditional return periods and drought intensity–area–frequency (I–A–F) curves. The I–A–F curves could be helpful in risk evaluation of droughts in the region.     

Construction of Intensity–Duration–Frequency (IDF) curves for precipitation at Lubumbashi,Congo, under the hypothesis of inadequate data

Abstract

Intensity–Duration–Frequency (IDF) curves for precipitation constitute a probabilistic tool and have proven useful in water resources management. In particular, IDF curves for precipitation enable questions on the extreme character of precipitation to be answered. The construction of IDF curves for precipitation is difficult or impossible in tropical areas due to the lack of long-term extreme precipitation data. A technique is proposed to overcome this shortcoming by combining limited high-frequency information on rainfall extremes with long-term daily rainfall information. It may be regarded as an extension of Koutsoyiannis' approach. Using this technique, IDF curves for precipitation are produced for Lubumbashi in Congo.

Citation Van de Vyver, H. & Demarée, G. R. (2010) Construction of Intensity–Duration–Frequency (IDF) curves for precipitation at Lubumbashi, Congo, under the hypothesis of inadequate data. Hydrol. Sci. J. 55(4), 555–564.     

Soil characterization of Tınaztepe region (İzmir/Turkey) using surface wave methods and nakamura (HVSR) technique

To determine the shear wave velocity structure and predominant period features of T?naztepe in ?zmir, Turkey, where new building sites have been planned, active–passive surface wave methods and single-station microtremor measurements are used, as well as surface acquisition techniques, including the multichannel analysis of surface waves (MASW), refraction microtremor (ReMi), and the spatial autocorrelation method (SPAC), to pinpoint shallow and deep shear wave velocity. For engineering bedrock (V _s > 760 m/s) conditions at a depth of 30 m, an average seismic shear wave velocity in the upper 30 m of soil (AV_s30) is not only accepted as an important parameter for defining ground behavior during earthquakes, but a primary parameter in the geotechnical analysis for areas to be classified by V _s30 according to the National Earthquake Hazards Reduction Program (NEHRP). It is also determined that Z1.0, which represents a depth to V _s = 1000 m/s, is used for ground motion prediction and changed from 0 to 54 m. The sediment–engineering bedrock structure for T?naztepe that was obtained shows engineering bedrock no deeper than 30 m. When compared, the depth of engineering bedrock and dominant period map and geology are generally compatible.     

Soil characterization of T?naztepe region(?zmir/Turkey) using surface wave methods and nakamura(HVSR) technique

To determine the shear wave velocity structure and predominant period features of T?naztepe in ?zmir, Turkey, where new building sites have been planned, active–passive surface wave methods and single-station microtremor measurements are used, as well as surface acquisition techniques, including the multichannel analysis of surface waves(MASW), refraction microtremor(Re Mi), and the spatial autocorrelation method(SPAC), to pinpoint shallow and deep shear wave velocity. For engineering bedrock(V_s 760 m/s) conditions at a depth of 30m, an average seismic shear wave velocity in the upper 30m of soil(AV_s30) is not only accepted as an important parameter for defining ground behavior during earthquakes, but a primary parameter in the geotechnical analysis for areas to be classified by V_s30 according to the National Earthquake Hazards Reduction Program(NEHRP). It is also determined that Z1.0, which represents a depth to V_s = 1000m/s, is used for ground motion prediction and changed from 0 to 54m. The sediment–engineering bedrock structure for T?naztepe that was obtained shows engineering bedrock no deeper than 30m. When compared, the depth of engineering bedrock and dominant period map and geology are generally compatible.     

High-temperature emplacement of the Cerro Galán and Toconquis Group ignimbrites (Puna plateau,NW Argentina) determined by TRM analyses

Estimates of pyroclastic flow emplacement temperatures in the Cerro Galán ignimbrite and Toconquis Group ignimbrites were determined using thermal remanent magnetization of lithic clasts embedded within the deposits. These ignimbrites belong to the Cerro Galán volcanic system, one of the largest calderas in the world, in the Puna plateau, NW Argentina. Temperature estimates for the 2.08-Ma Cerro Galán ignimbrite are retrieved from 40 sites in 14 localities (176 measured clasts), distributed at different distances from the caldera and different stratigraphic heights. Additionally, temperature estimates were obtained from 27 sample sites (125 measured clasts) from seven ignimbrite units forming the older Toconquis Group (5.60–4.51 Ma), mainly outcropping along a type section at Rio Las Pitas, Vega Real Grande. The paleomagnetic data obtained by progressive thermal demagnetization show that the clasts of the Cerro Galán ignimbrite have one single magnetic component, oriented close to the expected geomagnetic field at the time of emplacement. Results show therefore that most of the clasts acquired a new magnetization oriented parallel to the magnetic field at the moment of the ignimbrite deposition, suggesting that the clasts were heated up to or above the highest blocking temperature (T _b) of the magnetic minerals (T _b = 580°C for magnetite; T _b = 600–630°C for hematite). We obtained similar emplacement temperature estimations for six out of the seven volcanic units belonging to the Toconquis Group, with the exception of one unit (Lower Merihuaca), where we found two distinct magnetic components. The estimation of emplacement temperatures in this latter case is constrained at 580–610°C, which are lower than the other ignimbrites. These estimations are also in agreement with the lowest pre-eruptive magma temperatures calculated for the same unit (i.e., 790°C; hornblende–plagioclase thermometer; Folkes et al. 2011b). We conclude that the Cerro Galán ignimbrite and Toconquis Group ignimbrites were emplaced at temperatures equal to or higher than 620°C, except for Lower Merihuaca unit emplaced at lower temperatures. The homogeneity of high temperatures from proximal to distal facies in the Cerro Galán ignimbrite provides constraints for the emplacement model, marked by a relatively low eruption column, low levels of turbulence, air entrainment, surface–water interaction, and a high level of topographic confinement, all ensuring minimal heat loss.     

Bemerkungen zu T.E. Aurén,Studies of Solar Radiation 1951

Zusammenfassung Die vonT. E. Aurén entwickelte Methode, aus einer grossen Anzahl von Messungen der Totalstrahlung der Sonne Kurven der mittleren Maxima zu gewinnen, wird befürwortet. Diese Kurven repräsentieren die für jeden Messort charakteristische, optimale Durchlässigkeit der Atmosphäre. Sie können daher auch als strahlungsklimatischer Parameter verstanden werden, sei es etwa als Intensität des solaren Strahlungsstromes bei bestimmten Höhenwinkeln, oder als Tagessummen usw.     

P and S velocity structures of the Santorini–Coloumbo volcanic system (Aegean Sea,Greece) obtained by non-linear inversion of travel times and its tectonic implications

One of the most prominent tectonic features of the Eastern Mediterranean region is the Hellenic volcanic arc in the Southern Aegean Sea, with the Santorini Island being one of the most active volcanic centers. Recent seismic studies show that the main seismic activity of the Santorini volcanic center is strongly associated with the volcanic processes, as well as with the seismo-tectonic regime of the broader Southern Aegean Sea area. The main cluster of local seismicity is located near the northeastern edge of the Santorini Island, beneath the Coloumbo Reef, which is a submarine volcanic seamount of the Santorini Island volcanic system.     

Insights into eruption dynamics from textural analysis: the case of the May, 2008, Chaitén eruption

The May, 2008, Chaitén (southern Chile) eruption was characterized by several explosive events, each associated with plumes which reached up to about 19?km above sea level on May 6. A study of the textural and physical features of the juvenile clasts erupted during the climactic phase of the 2008 eruption of Chaitén is presented. Pumice clasts show unimodal density distribution (main mode at 600?kg/m³), average vesicularity of about 69?%, a glassy groundmass with no microcrystals, and vesicles with dimension between ～1?μm and ～2?mm. They also show a unimodal vesicle size distribution with most frequent vesicle size in the range 0.05–0.08?mm and an estimated vesicle number density of 1.3?±?0.5?×?10⁵?mm^?3 related to a rapid nucleation event produced during the late phases of magma rise. This is confirmed by the absence of microcrystals that could otherwise have delayed vesicle formation and allowed the magma to maintain a low viscosity and a supersaturation in volatiles. Vesiculation and fragmentation were triggered by a sudden decompression of the melt associated with the opening of the volcanic conduit (～10?MPa?s^?1).     

A source extent analysis of the Lancang earthquake(M_s=7.6)of 1988

ＡｓｏｕｒｃｅｅｘｔｅｎｔａｎａｌｙｓｉｓｏｆｔｈｅＬａｎｃａｎｇｅａｒｔｈｑｕａｋｅ（Ｍｓ＝７．６）ｏｆ１９８８ＳＩ－ＨＵＡＺＨＥＮＧ（郑斯华）ＪＩＡＮＹＡＮＧ（杨健）ＣｅｎｔｅｒｆｏｒＡｎａｌｙｓｉｓａｎｄｐｒｅｄｉｃｔｉｏｎ,ＣｈｉｎａＳｅｉｓ...     

Reconstruction of the volcanic history of the Tacámbaro-Puruarán area (Michoacán, México) reveals high frequency of Holocene monogenetic eruptions

The 690?km² Tacámbaro-Puruarán area located at the arc-front part of the Michoácan-Guanajuato volcanic field in the Trans-Mexican Volcanic Belt (TMVB) records a protracted history of volcanism that culminated with intense monogenetic activity in the Holocene. Geologic mapping, ⁴⁰Ar/³⁹Ar and ¹⁴C radiometric dating, and whole-rock chemical analyses of volcanic products provide insights to that history. Eocene volcanics (55–40?Ma) exposed at uplifted blocks are related to a magmatic arc that preceded the TMVB. Early TMVB products are represented by poorly exposed Pliocene silicic domes (5–2?Ma). Quaternary (<2?Ma) volcanoes (114 mapped) are mainly scoria cones with lavas (49 vol.%), viscous lava flows (22 vol.%), and lava shields (22 vol.%). Erupted products are dominantly either basaltic andesites (37 vol. %), or andesites (17 vol.%), or span across both compositions (28 vol.%). Basalts (9 vol.%), dacites (4 vol.%), shoshonites (2 vol.%), and other alkali-rich rocks (<3 vol.%) occur subordinately. Early-Pleistocene volcanism was bimodal (dacites and basalts) and voluminous while since 1?Ma small-volume eruptions of intermediate magmas have dominated. Higher rates of lithospheric extension in the Quaternary may have allowed a larger number of small, poorly evolved dikes to reach the surface during this period. Eruptive centers as old as 1.7?Ma are aligned in a NE direction parallel to both, basement faults and the direction of regional compressive stress, implying structural control on volcanic activity. Data suggest that volcanism was strongly pulsatory and fed by localized low-degree partial melting of mantle sources. In the Holocene, at least 13 eruptions occurred (average recurrence interval of 800?years). These produced ~3.8?km³ of basaltic andesitic to andesitic magma and included four eruptions dated at ~1,000; 4,000; 8,000; and 11,000?years bc (calibrated ¹⁴C ages). To date, this is one of the highest monogenetic eruption frequencies detected within such a small area in a subduction-related arc-setting. These anomalous rates of monogenetic activity in an area with thick crust (>30?km) may be related to high rates of magma production at depth and a favorable tectonic setting.     

Catalogue of earthquakes (September-November, 1993)

Ｃａｔａｌｏｇｕｅ　ｏｆ　ｅａｒｔｈｑｕａｋｅｓ　（Ｓｅｐｔｅｍｂｅｒ－Ｎｏｖｅｍｂｅｒ，１９９３）（陈培善）Ｃａｔａｌｏｇｕｅｏｆｅａｒｔｈｑｕａｋｅｓ（Ｓｅｐｔｅｍｂｅｒ－Ｎｏｖｅｍｂｅｒ，１９９３）￥Ｐｅｉ－ＳｈａｎＣＨＥＮ（Ｉｎｓｔｉｔｕｔｅ...     

Catalogue of earthquakes (June-August,1994)

Ｃａｔａｌｏｇｕｅｏｆｅａｒｔｈｑｕａｋｅｓ（Ｊｕｎｅ－Ａｕｇｕｓｔ，１９９４）Ｐｅｉ－ＳｈａｎＣＨＥＮ（陈培善）（ＩｎｓｔｄｕｔｅｏｆＧｅｏｐｈｙｓｉｃｓｒ，ＳｔａｔｅＳｅｄｍｏｌｏｇｉｃａｌＢｕｒｅａｕ，Ｂｅｉｊｉｎｇ１０００８１，Ｃｈｉｎａ）Ｉ...