What is a “tectonic analog”?  (1) Mmax implies large L, W.  Most SCRs are best examined with regional geologic and tectonic maps (1:2,500,000 – 1:10,000,000 scale)  (2) Large tectonic elements (rifts, passive margins, orogens, cratons) are easiest to identify on regional maps.  (1) + (2): Do any kinds of large tectonic elements have characteristic fault styles that favor large rupture L, W?  (Most useful if represented in CEUS and adjacent Canada)  Mmax = large Mo release on large faults Figure A13–1

Figure A13–2

Characteristic fault styles  Extensional plate motions (rifts, passive margins)  Rift-parallel & margin-parallel faults are long  Steep dips, deep penetration (alkaline igneous rocks)  Large L, W: large Mo  Thick, restricted sandstones, then widespread limestones  Contractional plate motions (orogens)  Low-dip thrust faults, long, wide, above most seismicity  Faults steepen into hot cores (healing, folding, offsetting faults)  Large L, W, where low dips; smaller W where steeper: smaller Mo?  Sandstones, shales, limestones; thicker closer to rising mountains  Precambrian plate motions (cratons)  Old: rifting, folding, thrusting overprinted on each other repeatedly  Faults of all L and orientations, older faults can be healed and deformed; small effective L, W: smaller Mo  Tectonically quiet: few associated sedimentary, igneous rocks Figure A13–3

Figure A13–4

Analogs  Rifts & margins have distinctive fault styles and associated igneous and sedimentary rocks.  Ditto for orogens. Ditto for cratons.  Rifts & margins are recognizable from one SCR to another, ditto for orogens, cratons  Rifts & margins, orogens, cratons are distinguishable from each other within same SCR  Differences within an SCR >> differences between SCRs  Faults heal so faulting age matters Figure A13–5