[1] Knowledge of the controls on temperature distributions at subduction zones is critical for understanding a wide range of seismic, metamorphic, and magmatic processes. Here, we present the results of $220 thermal model simulations covering the majority of known subduction zone convergence rates, incoming plate ages, and slab dips. We quantify the thermal effects of fluid circulation in the subducting crust by comparing results with and without advective heat transfer in the oceanic crustal aquifer. We find that hydrothermal cooling of a subduction zone is maximized when the subducting slab is young, slowly converging, steeply dipping, and the crustal aquifer is ventilated near the trench. Incoming plate age is one of the primary controls on the effectiveness of advective heat transfer in the aquifer, and the greatest temperature effects occur with an incoming plate <50 Ma. The thermal effects of fluid circulation decrease dramatically with increasing age of the incoming plate. Temperatures in the Cascadia, Nankai, southern Chile, Colombia/Ecuador, Mexico, and Solomon Islands subduction zones are likely strongly affected by fluid circulation; for these systems, only thermal models of Cascadia and Nankai have included fluid flow in subducting crust.

Delineating rupture areas of subduction zone earthquakes is necessary for understanding the controls on seismic and aseismic slip. For the largest recorded earthquake, the 1960 Chile event with moment magnitude 9.5, the rupture area is only loosely defined due to limitations in the global seismic network at the time. The rupture extends~900 km along strike. Coastal deformation is consistent with either a constant rupture width of~180-200 km along the entire length or a narrower (~115 km) rupture in the southern half. A southward narrowing of the seismogenic zone has been hypothesized to result from warming of the subduction zone to the south, where the subducting plate is younger. We present results of thermal models at 36°S, 38°S, 43°S, and 45°S to examine potential along-strike changes in thermal state. Models most consistent with observed surface heat flux include fluid circulation in the oceanic crust that advects heat to the ocean. This ventilated hydrothermal circulation preferentially cools transects with young subducting lithosphere; frictional heating preferentially warms transects with older subducting lithosphere. The combined effects of frictional heating and hydrothermal circulation increase décollement temperatures in the 36°S and 38°S transects by up to~155°C and decrease temperatures in the 45°S transect by up to~150°C. In our preferred models, décollement temperatures 200 km landward of the trench in all four transects arẽ 350-400°C. This is consistent with a constant~200 km wide seismogenic zone for the 1960 M w 9.5 rupture, with decreasing slip magnitude in the southern half of the rupture.

Tsunami earthquakes, events that generate larger than expected tsunami and are deficient in high‐frequency seismic radiation, are rare but hazardous to coastal populations. One model for these events is shallow rupture through low‐strength materials. We calculate seismic moment, corner frequency, and stress drop for 216 earthquakes (2.1 < Mw < 4.7, November 2005 to June 2006) within and external to the 1992 Nicaragua tsunami earthquake rupture zone to test the hypothesis that differences in fault zone properties defined the limits of the 1992 tsunami rupture zone and continue to produce spatial variations in earthquake source properties. Mean stress drop of events within the rupture area is 1.2 MPa, and 5.5 MPa for events just outside of the rupture zone, with similar magnitude earthquakes in each group. Our results demonstrate different source parameter characteristics for microseismicity in the region of a past tsunami earthquake.