## 4 Discussion  
Wedge earthquakes are also related to subduction-related surface topography formation (e.g., [41]) because plume/melt upwelling affects seismotectonics and orogenesis spontaneously. According to a numerical modeling study of a subduction zone, [PERSON] [40] proposed that subduction at a shallow angle facilitates the uplift of a continental plateau, while subduction at a large angle contributes to the formation of a mountain or island. Previous studies also widely support that small angle subduction prefers the formation of a wide continental high topography, as a small portion of the continental crust closest to the margin possibly partitions due to the shallow subduction dip (e.g., [42]). In Alaska,  
Figure 4: Wedge earthquakes in Alaska. Slab color indicates water content (wt %) distribution. The colored spheres indicate all M > 3 earthquakes (IRIS) in the North American plate from 1 January 2000 to December 2010 and all M > 5.5 earthquakes from 1 January 1900 to December 2000 (Centennial Database). The black curve on the surface represents the coast. Red cones indicate active arc volcanoes [40]. Yellow ellipses indicate clustered continental wedge earthquakes. (**a**) View of the 3D model from the west. (**b**) View of the 3D model from the east. shallow subduction in south-central Alaska results in fluid/molten upwelling landward, where the Alaska range uplifts and evolves landward. The steep subduction in the Alaska Peninsula causes mineral upwells limited in a narrow cross-strike width, which results in the formation of island arcs such as the Alaska Peninsula and the Aleutian Islands. Small dip angle subduction of the cold lithosphere facilitates the fluid/melt rising in the continental wedge compared with the large dip angle oceanic plate. In addition, plate collision and subsequent upward extruding force both contribute to the formation of magma chambers or transcrustal magmatic that originates from melt processing in the deep crust [43], which facilitates the construction of an uplifted continental plateau. A broad forearch high, such as a large mountain system or continental plateau, an accretionary prism, and a shallow trench, is evidenced by south-central Alaska. On the other hand, when the slab dip angle increases to 20\({}^{\circ}\)-30\({}^{\circ}\), mountains or island arcs are generated due to a limited cross-arc width for slab metamorphism and exhumann to the surface close to the trench, such as the Aleutian and Alaska Peninsula. The frictional strength of the sediments and serpentinized peridotite exert a large control on the dip angle of the subduction interface at seismogenic depths [44]. In the high friction case, the subduction interface is steep, the trench is deeper, and the accretionary prism, forearch high, and basin are all absent [44]. In Alaska, the dip angle is greatly determined by the plate age (via the temperature and density comparison between two coupled plates), as shown in Figure 5. The reason that a broad forearch high is constructed by a shallow dip angle may be attributed to the extrusion effect brought by the incoming oceanic plate and the subsequent upwelling controlled by the dip angle. The Alaska Peninsula and the Fox Islands in the Aleutian Islands characterize an older oceanic plate age of approximately 50 Myr and a larger dip angle (12\({}^{\circ}\)-27\({}^{\circ}\)) at Moho depth compared with the Alaska range uplift in south-central Alaska, caused by a younger plate (approximately 40 Myr) and a smaller dip angle (7.7\({}^{\circ}\)). Consequently, wedge earthquakes in Alaska are characterized by a distance to the trench transitioning from small (steep subduction) to large (flat subduction), which is likely determined by the slab surface depth of 60-100 km, where the slab is fully dehydrated and subsequently hydrates the above mantle wedge and crust, generating clustered wedge earthquakes in Alaska. Slab dehydration induces plume upwelling, which not only facilitates wedge seismic events but also alters the surface topography over a geological time scale.