Microzonation of the city of Basel

During the past centuries, the city of Basel has suffered damage caused by earthquakes. One extraordinary event described in historical documents is the strong earthquake which occurred in 1356. The 1356 event, one of the strongest earthquakes in northwest-Europe, was obviously much stronger than the low-magnitude earthquakes observed in the area during this century. Even though the present seismicity in the Basel area is low, strong earthquakes have to be expected due to the city's geographical location close to the northern boundary of the African-European convergence zone, at the southern end of the Rhinegraben. A crucial step towards preparedness for future events and mitigation of earthquake risk involves a microzonation study of the city. The study is carried out in three steps: (1) a detailed mapping of the geology and geotechnical properties of the area, (2) measurement, interpretation and modelling of ambient noise data, and (3) numerical modelling of expected ground motions during earthquakes. A qualitative microzonation of the centre of Basel is presented, and it is discussed by comparing it to the historically reported damage of the 1356 earthquake.     

Earthquake scenarios for the city of Basel

Damage scenarios for Basel (Switzerland) are presented, based on a microzonation study and on the distribution of buildings in the different districts of the city. Two reference scenarios are assumed, corresponding to an event with an intensity between VII and VIII and a return period of 475 years, and an event that simulates the 1356 Basel earthquake with an intensity of IX in the city. The overall building damage in the different districts ranges between 8 and 20% for the intensity VII–VIII scenario, while for the intensity IX scenario values range from 31 to 56%. The variation in building vulnerability class within the city and the variability of local ground conditions affect the overall damage significantly, so that their influence on earthquake damage can accumulate or cancel for single districts.     

Environmental Hazard Ranking of Chemicals Spilled in the Rhine River in November 1986

In 1986 a chemical spill took place from the Sandoz plant in Basel, Switzerland, into the Rhine River. Several chemicals entered the river and were transported downstream. In this paper we rank the environmental hazard of eight chemicals, Disulfoton, Dinitroorthocresol, Propetamphos, Thiometon, Parathion, Etrimphos, Metoxuron and Fenitrothion found in the German section of the Rhine River. Five attributes related to the toxicity, physio-chemical characteristics and fate are used to rank the chemicals. The fate attributes were derived using the fate model EXWAT. Two ranking methods were used and results were compared. One method is based on the standardization of the data into attributes and aggregation into an index. The second method allows one to visually compare chemicals based on a large number of test results which might otherwise be very confusing when displayed in a table form: The Hasse diagram is an effective graphical display of data difficult to understand otherwise. Results by both ranking methods show that these chemicals can be divided into two groups, the most hazardous include Dinitroorthocresol, Propetamphos and Parathion, and the least hazardous include Disulfoton, Thiometon, Etrimphos, Metoxuron and Fenitrothion.     

Versuch zur Charakterisierung atmosphärischer Kondensationskerne durch Koagulationsmessungen und durch Messungen bei verschiedenen Expansionen

Zusammenfassung Es wird versucht, örtliche und zeitliche Verschiedenheiten des Luftaerosols mit Hilfe von 2 Methoden zu erfassen:a) durch Koagulationsversuche bei einer in einem Ballon aufbewahrten Luftprobe durch regelmässige Messungen mit dem automatischen Kondensationskernzähler;b) durch Bestimmung der Kernzahl bei verschiedenen Expansionsdrucken während der Aufbewahrung einer Luftprobe. Solche Bestimmungen werden zur Zeit der maximalen nnd minimalen Kernzahl im Laufe eines Tages in Basel sowie in St. Moritz-Bad ausgeführt. Die Versuche sollen später, besonders vom meteorologischen Gesichtspunkt aus, ausgewertet werden.

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Summary The number of atmospheric condensation nuclei shows daily variations and also local differences. To test whether the nuclei are also different in quality and size two methods have been tried: Air was collected in a balloon and the coagulation followed by measuring the number of nuclei during 8 to 9 hours. Examples are given for air in Basel at 11 a.m. and at 4 a.m. Also differences are shown between the air in Basel (270 m) and St. Moritz-Bad at 1 800 m altitude. The coagulation of air samples was also studied with different expansion pressure up to 9 hours. All measurements were made with the automatic condensation nuclei counter. No definite conclusions are drawn but the value of these methods shall be studied expecially in connection with meteorological observations.

     

Kontinuierliche Zählung von Atmosphärischen Kondensationskernen in St. Moritz

Zusammenfassung 1)Mit dem automatischen Kondensationskernzähler sind Messungen in St. Moritz in den Jahren 1953–1954, während insgesamt 12 Monaten, durchgeführt worden. 2) Es wird der Tagesgang der Stundenmittel der Kernzahlen pro Monat, ferner dasselbe an trüben und sonnigen Tagen und an Tagen mit verschiedener Windrichtung untersucht. 3) Der Verlauf der Kernzahlkurve in 2 verschiedenen Stationen in Basel und in einer Station in St. Moritz wird verglichen.

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Summary 1) With the automatic Condensation Nucleus Counter the number of atmospheric condensation nuclei was recorded during 12 months in the years 1952, 1953 and 1954. 2) The daily variation in middle values per month, the daily variation on sunny and cloudy days, and the daily variation at different wind directions are described. 3) The records in two different places in Basel and in St. Moritz are compared.

     

Kontinuierliche Messung atmosphärischer Kondensationskerne (Vorläufige Ergebnisse mit dem registrierenden Kernzähler in Basel)

Zusammenfassung Nachdem an Hand weiterer Versuche auf die physiologische und bioklimatische Bedeutung der Kondensationskerne hingewiesen wurde, werden die in den Monaten Januar bis März 1953 an der Astronomisch-Meteorologischen Anstalt in Basel mit dem automatischen Kernzähler durchgeführten Registrierungen der Kernzahlen verarbeitet, wobei auf Grund von Stundenmitteln der Tagesgang der Kernzahlen, sowie ihre Abhängigkeit von Windgeschwindikeit, Windrichtung, Sonnenschein, relative Feuchtigkeit, Sichtweite und Luftmassen untersucht und diskutiert wurden.

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Summary After referring, on the basis of further experiments, to the physiological and bioclimatic importance of the condensation nuclei, the recording performed during the months of January till March 1953 at the Institute for Astronomy and Meteorology, in Basel, with the automatic nucleus-counting apparatus are digested; at the same time, by means of hourly averages, the daily variations of the nucleus numbers as well as their dependence on the speed and direction of the wind, sunshine, relative humidity, distance of visibiliy, and air mass are examined and discussed.

     

The variation of crustal thickness across the Swiss Alps based on gravity and explosion seismic data

Summary Recently determined gravity anomalies along the NW-SE oriented Swiss Geotraverse from Basel to Bellinzona are used in combination with seismic refraction data to deduce a crustal section across the Swiss Alps. Topographic, Bouguer, free air, isostatic and geological corrections were applied to the data. Geological features considered in the corrections are the Swiss Molasse basin filled with sediments and the Ivrea body of high-density material. The resultant Bouguer anomaly over the Gotthard massif is 130 mgal lower than the Bouguer anomaly at the northern end of the profile near Basel. The Alpine region is associated with negative isostatic anomalies down to –20 mgal. The crustal thickness is found to increase gradually from the northern end of the profile (thicknessH=30 km) towards the Helvetic nappes at the northern margin of the Alps (H=38 km) and more rapidly towards the Gotthard massif (H=50 km) and further south to Biasca down to a depth of 58 km. From Biasca southward the crustal thickness thins quite rapidly to reach a depth of 30 km at the southern end of the profile near Bellinzona. Thus the Alps have a distinct asymmetric crustal root whose maximum thickness is almost twice the average crustal thickness in Central Europe. With the Mohorovii-discontinuity deduced from seismic observations an average constant density contrast of –0.33 gcm^–3 is found between the lower crust and upper mantle underneath the Alps.Institut für Geophysik, ETH Zürich, Contribution No. 130.     

Ergebnisse der Registrierungen der Zahl der Kondensationskerne in Basel und seiner nächsten Umgebung

Zusammenfassung In Fortsetzung früher mitgeteilter Ergebnisse von Registrierungen mit demVerzár'schen Kernzähler in Basel wird der Einfluss der Luftmassenwechsel, des Sonnenscheins und der Niederschläge auf den Kerngehalt untersucht. Weiterhin werden die Ergebnisse gleichzeitiger Registrierungen im Stadtinnern und am Stadtrand, sowie am Stadtrand und einem Villenvorort eingehend diskutiert.Ein weiterer Vergleich zwischen Basel und Payerne ergibt Beziehungen zwischen den Tagesmitteln der Kernzahlen dieser fast 100 Km von einander entfernten Orte.

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Summary Continuing previously communicated results of recordings with theVerzár nuclei counter at Basle the influences of changes of air masses, of sunshine and precipitation on nuclei concentration are studied. Furthermore the results of simultaneous recordings in the centre of the city and on the outskirts, as well as on the out-skirts of the city and at a near-by village are thoroughly discussed. A further comparison between Basle and Payerne shows connections between daily means of nuclei concentration of these two towns, which are about 100 Km apart.

     

Reliability of Building Inventories in Seismic Prone Regions

A study on uncertainties in building inventory and vulnerability assessment for the city of Basel, Switzerland a moderate hazard but high-risk area is presented. Emphasis is put on the special conditions and demands on the data assessment procedure in such an environment. The building information was assessed from the sidewalk using a method similar to that proposed in FEMA-154. With only three persons working for two weeks, about 10% of the citys building stock was assessed. The quality of the dataset was tested by using pre-existing reference data. These tests revealed patterns of misinterpreted structural information; important features like the floor type in URM buildings were difficult to identify.Six methods are proposed to derive building vulnerability from the collected structural information using the definitions of EMS98. The variation between the individual results was investigated in detail. A sample earthquake scenario with intensity IX in the city of Basel is used to demonstrate the influence of uncertainty in the inventory on the scenario results. The range of variation in the results is huge. Overall damage in the six scenarios differed by up to 27%. The amount of collapsed buildings in the historical part of the city comprised between 28% in the worst case and 3% in the best. There is a distinct influence of the inspectors opinion visible in the scenario results, which introduces a remarkable uncertainty. This emphasizes the importance of reliable inventory assessments and makes uncertainty analysis in earthquake scenarios indispensable – especially in areas of moderate seismicity where observational data from earthquake damage is missing.     

Ergebnisse der Eineinhalbjährigen Registrierungen der Anzahl der Kondensationskerne in Basel

Zusammenfassung Anhand von eineinhalbjährigen Registrierungen der Kernzahlen (nachVerzár) in Basel wird der Jahresgang und Tagesgang der Kernzahlen besprochen. Die Abhängigkeit von der Windrichtung und Windgeschwindigkeit wird eingehend untersucht. Es wird ein Wochenrythmus der Kernzahlen nachgewiesen und die Häufigkeit der Kerne bei verschiedernartigen Luftmassen untersucht. Anschliessend wird über gleichzeitige Registrierungen im Stadtinnern und am Stadtrand kurzberichtet.

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Summary On recordings of nuclei-countings (accordingVerzár) over a period of one and a half year et Basle the yearly and daily variations of the number of nuclei are discussed. The influence of wind direction and wind velocity on the number of nuclei are studied. A weekly periodicity of nuclei numbers is shown and the abundance of nuclei in different air masses is studied. Finally the results of simultaneous recordings in the center and at the border of the city are communicated.

     

Application of microseismic multiplet analysis to the Basel geothermal reservoir stimulation events

The stimulation of a geothermal well in Basel, Switzerland produced a distribution of microseismic event locations with an overall alignment in the direction of the maximum horizontal stress. Fault plane solutions of individual larger events indicated movements on fracture planes at an angle to the maximum horizontal stress that could not be reliably interpreted from the event locations. To obtain higher resolution images of the microseismic event locations, events with similar waveforms have been identified by multiplet analysis. A number of receivers were used in the multiplet processing to ensure each multiplet is represented by a unique group of waveforms. The location accuracy within each multiplet has been significantly improved using cross‐correlation to refine the shear‐wave traveltime picks. The distribution of events within each multiplet can be interpreted as being due to movements on a single fracture or a number of near parallel fractures. It is shown that whilst the overall distribution of events is around the direction of the maximum horizontal stress, the individual multiplets representing fracture planes have a variety of azimuths and dips.     

Using Estimated Risk to Develop Stimulation Strategies for Enhanced Geothermal Systems

Enhanced geothermal systems (EGS) are an attractive source of low-carbon electricity and heating. Consequently, a number of tests of this technology have been made during the past couple of decades, and various projects are being planned or under development. EGS work by the injection of fluid into deep boreholes to increase permeability and hence allow the circulation and heating of fluid through a geothermal reservoir. Permeability is irreversibly increased by the generation of microseismicity through the shearing of pre-existing fractures or fault segments. One aspect of this technology that can cause public concern and consequently could limit the widespread adoption of EGS within populated areas is the risk of generating earthquakes that are sufficiently large to be felt (or even to cause building damage). Therefore, there is a need to balance stimulation and exploitation of the geothermal reservoir through fluid injection against the pressing requirement to keep the earthquake risk below an acceptable level. Current strategies to balance these potentially conflicting requirements rely on a traffic light system based on the observed magnitudes of the triggered earthquakes and the measured peak ground velocities from these events. In this article we propose an alternative system that uses the actual risk of generating felt (or damaging) earthquake ground motions at a site of interest (e.g. a nearby town) to control the injection rate. This risk is computed by combining characteristics of the observed seismicity of the previous 6 h with a (potentially site-specific) ground motion prediction equation to obtain a real-time seismic hazard curve; this is then convolved with the derivative of a (potentially site-specific) fragility curve. Based on the relation between computed risk and pre-defined acceptable risk thresholds, the injection is increased if the risk is below the amber level, decreased if the risk is between the amber and red levels, or stopped completely if the risk is above the red level. Based on simulations using a recently developed model of induced seismicity in geothermal systems, which is checked here using observations from the Basel EGS, in this article it is shown that the proposed procedure could lead to both acceptable levels of risk and increased permeability.     

Aseismic negative dislocation model and deformation analysis of crustal horizontal movement during 1999~2001 in the northeast margin of Qinghai-Xizang block

Introduction So small is the hypocenter area of strong earthquake, but its formation is controlled by time-space evolution of present-day crustal movement in wider-range area, and related to motion and deformation of active blocks and their boundary faults. Aseismic negative dislocation model presented by Matsuura, et al (1986) is that, the relative motion between blocks driven by present-day crustal movement may be partly locked at the block …     

Deriving fragility functions from bilinearized capacity curves for earthquake scenario modelling using the conditional spectrum

The development of fragility curves to perform seismic scenario-based risk assessment requires a fully probabilistic procedure in order to account for uncertainties at each step of the computation. This is especially true when developing fragility curves conditional on an Intensity Measure that is directly available from a ground-motion prediction equation. In this study, we propose a new derivation method that uses realistic spectra instead of design spectral shapes or uniform hazard spectra and allows one to easily account for the features of the site-specific hazard that influences the fragility, without using non-linear dynamic analysis. The proposed method has been applied to typical school building types in the city of Basel (Switzerland) and the results have been compared to the standard practice in Europe. The results confirm that fragility curves are scenario dependent and are particularly sensitive to the magnitude of the earthquake scenario. The same background theory used for the derivation of the fragility curves has allowed an innovative method to be proposed for the conversion of fragility curves to a common IM (i.e. spectral acceleration or PGA). This conversion is the only way direct comparisons of fragility curves can be made and is useful when inter-period correlation cannot be used in scenario loss assessment. Moreover, such conversion is necessary to compare and verify newly developed curves against those from previous studies. Conversion to macroseismic intensity is also relevant for the comparison between mechanical-based and empirical fragility curves, in order to detect possible biases.     

Aseismic negative dislocation model and deformation analysis of crustal horizontal movement during 1999——2001 in the northeast margin of Qinghai-Xizang block

Through numerical simulation for GPS data, aseism/c negative dislocation model for crustal horizontal movement during 1999-2001 in the northeast margin of Qinghai-Xizang block is presented, combined with the spatial distri-bution of apparent strain field in this area, the characteristics of motion and deformation of active blocks and their boundary faults, together with the place and intensity of strain accumulation are analyzed. It is shown that: a) 9 active blocks appeared totally clockwise motion from eastward by north to eastward by south. Obvious sinistral strike-slip and NE-NEE relative compressive motion between the blocks separated by Qilianshan-Haiyuan fault zone was discovered; b) 20 fault segments (most of them showed compression) locked the relative motion between blocks to varying degrees, among the total, the mid-east segment of Qilianshan fault (containing the place where it meets Riyueshan-Lajishan fault) and the place where it meets Haiyuan fault and Zhuanglanghe fault, more favored accumulation of strain. Moreover, the region where Riyueshan-Lajishan fault meets north boundary of Qaidam block may have strain accumulation to some degree, c) Obtained magnitude of block velocities and locking of their boundaries were less than relevant results for observation in the period of 1993-1999.     

The role of crust thickness in runoff generation from microbiotic crusts

Contrary to humid areas where runoff takes place following the saturation of the soil column, runoff in arid and semiarid zones takes place when rain intensities exceed the infiltration capability of the upper soil crust, whether physical crust or microbiotic crust (MC). This type of overland flow, known as Hortonian overland flow (HOF), is not fully understood, especially in the case of MC. In particular, little is known regarding the effect of crust thickness and its fine (silt and clay) content on runoff generation, with some scholars claiming that runoff generation is positively correlated with crust thickness and fine content. In an attempt to determine the effect of crust thickness and to assess the role played by the silt and clay on runoff generation, a set of field and lab experiments were undertaken on MCs inhabiting sand dunes in the Negev Desert (Israel). These included sprinkling experiments coupled with measurements of the physical (thickness, silt and clay) and biological (chlorophyll, protein, total carbohydrates) properties of 0.5–10‐mm‐thick crusts. The data showed that runoff generation took place on surfaces as thin as ~0.5–0.7 mm only, and was not correlated with the fine (silt and clay) content. The implications for HOF and for arid ecosystems are discussed. Copyright © 2014 John Wiley & Sons, Ltd.     

Submarine basaltic volcanism: Morphometric parameters for discriminating hyaloclastites from hyalotuffs

Hyaloclastites are volcaniclastic rocks generated by non-explosive granulation of volcanic glass which takes place when basaltic magmas are quenched by contact with water; hyaloclastites are common products of deep submarine basaltic central volcanoes (seamounts and guyots). We suggested (Honnorlz, 1966) calling hyalotuffs the actual pyroclastic rocks which are generated by phreatomagmatic and phreatic explosions taking place when basaltic volcanoes crupt in shallow waters; hyalotuffs are restricted to shallow subaqueous conditions since no volcanic explosion can occur in deep seas. The distinction between hyaloclastites and hyalotuffs is therefore a useful tool when reconstructing the paleogeography of ancient submarine volcanic edifices and the mechanism by which their lavas were emplaced. We propose using two sets of morphometric parameters to discriminate the hyaloclastites from the hyalotuffs. The granules making up these two volcaniclastic rock types plot in different areas of either 1) a ternary diagram the apexes of which represent the grain planarity (P), convexity (V) and concavity (C) % («roundness» according to Szadeczky-Kardoss); or 2) a binary diagram relating the number of grain corners (N) to their planarity (P) %.     

Lunar Tides in the Mesopause Region Obtained from Summer Temperature of the Hydroxyl Emission Layer

Geomagnetism and Aeronomy - The summer mesopause region (altitudes of 82–92 km) is the coldest place in the Earth’s atmosphere; it is influenced by external effects, including lunar...