If the hanging wall of a dip-slip fault moves down with respect to the footwall, it is called a normal fault (Figure 3-7). Some of the faults off the coast of Oregon and Washington are left-lateral faults (Figure 4-1, following chapter). At a left-lateral fault, objects on the other side of the fault appear to move to your left (Figure 3-6). The San Andreas Fault is the world’s best-known example of a right-lateral fault (Figure 3-5a). If you stand on one side of a right-lateral fault, objects on the other side of the fault appear to move to your right during an earthquake (Figure 3-5a, b). There are two kinds of strike-slip fault, right-lateral and left-lateral. If the hanging wall moves sideways, parallel with the Earth’s surface, as shown in Figure 3-3, 3-5, and 3-6, the fault is called a strike-slip fault. If the hanging wall moves up or down during an earthquake, the fault is called a dip-slip fault (Figure 3-4). Valuable ore deposits are commonly found in fault zones, and miners working underground along a fault zone find themselves standing on the footwall, with the hanging wall over their heads. These are terms that were first coined by miners and prospectors. Where the fault has a low dip or inclination, the rock above the fault is called the hanging wall, and the rock below the fault is called the footwall. Other faults dip at a low angle, so that the fault at the surface may be several miles away from the point on the Earth’s surface directly above the earthquake (Figure 3-4). Some faults are vertical so that an earthquake at 10 miles depth is directly beneath the fault at the surface where the rupture of the ground can be observed. Larger earthquakes may be accompanied by surface movement on these faults, damaging or destroying human-made structures under which they pass. But most of these faults are also exposed at the surface where they may be studied by geologists. ![]() Most damaging earthquakes form on faults at a depth of five miles or more in the Earth’s crust, too deep to be observed directly. ![]() Videos - Concise video lectures give background information on the Earth and plate tectonics for teaching how earthquakes happen and how they are studied.\) Software-Web-Apps - Stand alone software, interactive web tools, and downloadable apps to help you explore seismic data and earthquake topics. Posters - More than just wallpaper, these eye-catching, educative posters invite students to become minds-on with Earth's internal structure, earthquakes, seismic waves and more! Lessons - A step-by-step guide outlining what students will learn across one or more class periods, through a progression of activities, combined in a learning cycle, to achieve the desired student learning. Interactives - Uses interactive Flash (sfw) to illustrate fundamental concepts that are difficult to convey to learners through other means. IRIS offers a range of resources for students, educators and the general public.Īctivities - Bite-sized (5, 15, or 30 minute) demonstrations or student tasks tied to ‘Did You Know?’ questions to engage the learner.Īnimations - Concise animations that illustrate fundamental concepts that are difficult to convey to learners through other means (the real events may be too small, too large, too fast, too slow, or unsafe for the classroom).Ĭourse - A series of lessons that provide the structure for a semester-long undergraduate course.ĭemos - Quick teacher-lead activities (show-and-tell combined with an opportunity for learners to ponder, predict and discuss) to stimulate interest and convey a concept to learners.įact-Sheets- Single page, accessible, discussions of earthquake related topics.
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