Role of major terrestrial cratering events in dispersing life in the solar system

The larger and most energetic cratering events from comet and asteroid collisions with the Earth are probably associated with ejection of solid material faster than escape speeds every 100 Myr or so. Metre-sized boulders, we estimate, may have been ejected directly into Venus-crossing and perhaps Mars-crossing orbits from comet impacts at higher speeds and of larger mass, at least on 10 occasions in the last 3.5 Ga. Subsequent close encounters with Earth can also enable slower boulders to reach Mars-crossing orbits. Orbit perturbations from Mars and Jupiter would then have sent a fraction of the boulders to the outer planets and their icy satellite systems. In the so-called late bombardment epoch at 3.9 Ga, when primitive life was developing, ejection-causing impacts were much more frequent, at 30 per 0.1 Ga, yielding an increased probability of distributing seeds of terrestrial biology to the outer regions of the solar system.     

Precursory seismic quiescence

Seventeen cases of precursory seismic quiescence to mainshocks with magnitudes fromM _L=4.7 toM _S=8.0 are summarized. The amount of rate decrease ranges from 45% to 90%. The significance of these changes varies between 90% and 99.99%. The assumption that the background rate is approximately constant is fulfilled in most crustal volumes studied. All quiescence anomalies seem to have abrupt beginnings, and the rate during the anomalous period is fairly constant. The duration of the precursors ranges from 15 to 75 months, and it is not clear what factors determine that time. At least three successful predictions have been based on seismic quiescence. These cases have shown that mainshocks can be predicted based on quiescence, but they have also shown that the interpretation of the data in real time is difficult and nonunique. If a false alarm is defined as a period of quiescence with a significance level larger than a precursory quiescence in the same tectonic area, then we estimate, based on searches in four areas, that the false alarm rate may be on the order of 50%. Failure to predict may be expected in perhaps 50% of mainshocks, even in carefully monitored areas. Quiescence cannot be used as a precursor in tectonic environments with low seismic activity. Most characteristics of the phenomenon are still poorly defined, but data exist which probably permit at least a doubling of the presently available data on case histories.     

Die Interpretation von seismischen Refraktionsmessungen im Grenzfallc 0=0

Zusammenfassung Es wird im Anschluss an «Die Laufzeifunktion und ihre Interpretation in der Refraktionsseismik des einachsig inhomogenen Körpers» (4) die Interpretation von seismischen Refraktionsmessungen im Grenzfallc _o=0 eingehend behandelt.

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Summary In pursuance of «Die Laufzeifunktion und ihre Interpretation in der Refraktionsseismik des einachsig inhomogenen Körpers» (4) the special interpretation problem withc _o=0 is generally treated.

     

Das Problem des alpinen Wildflysch

Ohne Zusammenfassung     

Das Erdöl in Südbayern,geologische Stellung und Aussichten

Ohne Zusammenfassung     

Die neue Periode des Vesuvs

Ohne Zusammenfassung     

Ein Präzisionszeitskalenschreiber mit Dekadischer Frequenz-Unterteilung für Zeitmarkierung und Frequenzmessung

Zusammenfassung Es wird ein Präzisionszeitskalenschreiber mit fünffacherdekadischer Frequenzunterteilung für Zeitmarkierung und Frequenzmessung beschrieben, der aus RC-Schwingungskreisen mit Gasentladungsröhren besteht, in deren Entladungskreis sich eine Registrierschleife befindet. Der erste Kreis wird nach einem Uhrenprinzip durch eine Stimmgabel synchronisiert, wobei zwecks Erhöhung der Genauigkeit der Antrieb stets im Nulldurchgang erfolgt. Die Synchronisierung der weiteren Kreise erfolgt in der Weise, dass man dem Gitter des Kippschwingungskreises Spannungsstösse des davor liegenden Kippschwingungskreises überlagert, und zwar derart, dass die Zündung bei jedem zehnten überlagernden Stoss erfolgt. Die freien Kippschwingungen werden dabei zu erzwungenen zwangläufig synchronisierten Schwingungen. Die Frequenzunterteilung erfolgt in fünf Dekaden (1000, 100, 10, 1 und 0.1 Hertz).

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Summary A new time marking arrangement is described, developped by the Author, based on the application of thyratrons, synchronized by means of a tuning fork, and recording automatically a scale, which is subdivided in 5 decades and which works with extremely high exactness. The arrangement is synchronized by means of a clock principle.

     

Geological control of shallow gas and pockmarks in the Norwegian Channel; high resolution shallow subbottom profiling of small scale features

High resolution bathymetric and fine-scale parametric subbottom profiling along a line to the SW of Stavanger, Norway near the NE flank of the Norwegian Channel, show pockmarks clustered over neotectonic shallow fold structures in Quaternary sediments. Detailed profiles of the pockmarks indicate that they are collapsed gas seeps, rather than being collapse structures that followed doming and breaching with a more dramatic gas burst. The gentle folding and weak structures along the margin of a Mesozoic through Cenozoic sedimentary basin are probably due to differential uplift generating light compressional strain.     

Ein exakter Seismograph

Zusammenfassung Es wird ein exakter Seismograph beschrieben.

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Summary An exact seismograph is described.