Geometry of faceted spurs on an active normal fault : case study of the Central Wasatch Fault, Utah, U.S.A

Zuchiewicz, W. A.; McCalpin, J. P.

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Tytuł artykułu

Geometry of faceted spurs on an active normal fault : case study of the Central Wasatch Fault, Utah, U.S.A

Autorzy

Zuchiewicz W. A. , McCalpin J. P.

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Warianty tytułu

Geometria lic progów uskokowych aktywnego uskoku normalnego na przykładzie środkowego segmentu uskoku Wasatch w stanie Utah (U.S.A.)

Języki publikacji

Abstrakty

Faceted spurs preserved along the Central Wasatch Fault, north-central Utah, display different geometry and state of development. Geometric parametres of the largest faceted spurs that have been shaped since the Pliocene or early Quaternary appear to reflect lithological, structural and seismotectonic differentiation among the four fault segments studied (Brigham City, Weber, Salt Lake City, and Spanish Fork). The size of a faceted spur is a function of the distance between major canyons incised into mountain front and of the spur's height. Most of the canyons that truncate the western side of the Wasatch Mts. follow zones of weakness. Some of geometric parametres reflect the size of triangular facets (the numer and length of 1st-order interfluves), whereas dimensionless ratios (bifurcation and length ratios) are usually size-independent and are controlled by the rate of both seismotectonic uplift and erosional downcutting. The height of a faceted spur is a function of uplift whereas average slope may be affected by a variety of factors. On homogeneous bedrock the youngest facets are usually the steepest. Along the Wasatch fault such a relationship is, however, seldom observed due to either highly differentiated lithology of underlying rocks or the presence of subsidiary, high-angle normal faults that run parallel to the main fault zone, and dip towards the base of mountain front. The latter case resembles that of the Aegean-type fault scarps. The geometry of faceted spurs developed on differentiated bedrock, although controlled by seismotectonic uplift, is also strongly modified by rock resistance to erosion and by bedrock structure.

Artykuł charakteryzuje wpływ czynników tektonicznych oraz litologiczno-odpornościowych na morfologię lic progów uskokowych (triangular facets) w obrębie czterech segmentów uskoku Wasatch w północno- wschodniej części prowincji Basin and Range w stanie Utah. Dla charakterystyki topologicznej lic progów uskokowych zastosowaliśmy zmodyfikowaną klasyfikację Hortona-Strahlera. Lica progów uskokowych wykazują zróżnicowaną geometrię i stopień zachowania. Parametry geometryczne największych zespołów lic, kształtowanych od pliocenu lub wczesnego plejstocenu, odzwierciedlają różnice litologiczne i strukturalne oraz odmienne tempo ruchów sejsmotektonicznych pomiędzy czterema analizowanymi segmentami uskoku. Niektóre parametry (liczba i długość odcinków 1 rzędu, suma długości działów wodnych) odzwierciedlają rozmiary lica progu, podczas gdy wskaźniki bezwymiarowe (wskaźniki bifurkacji i długości) nie zależą od wielkości danej formy i są uwarunkowane tempem ruchów tektonicznych oraz prędkością rozcięcia erozyjnego. Wysokość poszczególnych lic jest funkcją wypiętrzenia tektonicznego, natomiast ich nachylenie może być efektem zarówno tektoniki, jak też zróżnicowania litologicznego i strukturalnego. Przeprowadzona analiza wykazuje, że geometria lic progów uskokowych w równym stopniu odzwierciedla tempo ruchów sejsmotektonicznych, jak też odporność i strukturę skał podłoża.

Słowa kluczowe

active normal fault faceted spurs Wasatch Fault Utah, U.S.A

Wydawca

Polskie Towarzystwo Geologiczne

Czasopismo

Annales Societatis Geologorum Poloniae

Rocznik

2000

Tom

Vol. 70, No. 3-4

Strony

231--249

Opis fizyczny

Bibliogr. 47 poz., fot., map., rys., tab., wykr.

Twórcy

autor

Zuchiewicz W. A.

witold@ing.uj.edu.pl

Institute of Geological Sciences, Jagiellonian University, 30-063 Kraków, Oleandry 2A

autor

McCalpin J. P.

mccalpin@geohaz.com

GEO-HAZ Consulting, Inc., P.O. Box 1377, Estes Park, CO 80517, U.S.A.

Bibliografia

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Typ dokumentu

Bibliografia

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