The Stafford fault system, located in the mid-Atlantic coastal plain of the eastern United States, provides the most complete record of fault movement during the past ~120 m.y. across the Virginia, Washington, District of Columbia (D.C.), and Maryland region, including displacement of Pleistocene terrace gravels. The Stafford fault system is close to and aligned with the Piedmont Spotsylvania and Long Branch fault zones. The dominant southwest-northeast trend of strong shaking from the 23 August 2011, moment magnitude M w 5.8 Mineral, Virginia, earthquake is consistent with the connectivity of these faults, as seismic energy appears to have traveled along the documented and proposed extensions of the Stafford fault system into the Washington, D.C., area. Some other faults documented in the nearby coastal plain are clearly rooted in crystalline basement faults, especially along terrane boundaries. These coastal plain faults are commonly assumed to have undergone relatively uniform movement through time, with average slip rates from 0.3 to 1.5 m/m.y. However, there were higher rates during the Paleocene–early Eocene and the Pliocene (4.4–27.4 m/m.y), suggesting that slip occurred primarily during large earthquakes. Further investigation of the Stafford fault system is needed to understand potential earthquake hazards for the Virginia, Maryland, and Washington, D.C., area. The combined Stafford fault system and aligned Piedmont faults are ~180 km long, so if the combined fault system ruptured in a single event, it would result in a significantly larger magnitude earthquake than the Mineral earthquake. Many structures most strongly affected during the Mineral earthquake are along or near the Stafford fault system and its proposed northeastward extension.

Abstract William Morris Davis (1888) considered the Appalachians to have had an important role in the development of geomorphology. He saw the systematic study of topography as largely of American origin, and suggested that there were two steps in its development. The first began about 1840 with the founding of the Eastern state surveys, during which geologists such as Lesley (1856) established the intimate relationship between topography and structure (in the broad sense) in the Appalachians. During this first step, according to Davis, topographic form was regarded as a completed product of extinct processes. Topography revealed structure, but it did not then reveal the long history that the structure has passed through. … The systematic relation of forms to structure, base level, and time; the change of drainage areas by contest of headwaters at divides; the revival of exhausted rivers by massive elevations of their drainage areas; all these consequences of slow adjustments were then unperceived (Davis, 1888, p. 14). The awareness of such principles, the second step in the advancement of the study of topography, came about largely as a result of the geological exploration of the western U.S., exemplified by the work of Powell (1875, 1876) and Gilbert (1877). Once this awareness came about, however, these principles were applied to the Appalachians; Davis (1888, p. 15) stressed the importance of the Appalachians in this second phase as well as the first: If it be true that the greater part of this second advance is American like the