Summary In the summer of 1998, project INDEPTH recorded a 400 km long NNW–SSE wide‐angle seismic profile in central Tibet, from the Lhasa terrane across the Banggong‐Nujiang suture (BNS) at about 89.5°E and into the Qiangtang terrane. Analysis of the P‐wave data reveals that (1) the crustal thickness is 65 ± 5 km beneath the line; (2) there is no 20 km step in the Moho in the vicinity of the BNS, as has been suggested to exist along‐strike to the east based on prior fan profiling; (3) a thick high‐velocity lower crustal layer is evident along the length of the profile (20–35 km thick, 6.5–7.3 km s−1); and (4) in contrast to the southern Lhasa terrane, there is no obvious evidence of a mid‐crustal low‐velocity layer in the P‐wave data, although the data do not negate the possibility of such a layer of modest proportions. Combining the results from the INDEPTH III wide‐angle profile with other seismic results allows a cross‐section of Moho depths to be constructed across Tibet. This cross‐section shows that crustal thickness tends to decrease from south to north, with values of 70–80 km south of the middle of the Lhasa terrane, 60–70 km in the northern part of the Lhasa terrane and the Qiangtang terrane, and less than 60 km in the Qaidam basin. The overall northward thinning of the crust evident in the combined seismic observations, coupled with the essentially uniform surface elevation of the plateau south of the Qaidam basin, is supportive of the inference that northern Tibet until the Qaidam basin is underlain by somewhat thinner crust, which is isostatically supported by relatively low‐density, hot upper mantle with respect to southern Tibet.

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Since 90 Ma, the nonmarine Salar de Atacama Basin has been the largest, deepest, and most persistent sedimentary basin of northern Chile. Integration of 200 km of two‐dimensional seismic reflection data with surface geological data clarifies Oligocene and Neogene evolution of the northern part of the basin. A normal fault with 6 ± 1 km of vertical separation controlled the western boundary of the basin during the accumulation of the Oligocene–lower Miocene Paciencia Group. The combination of this structure, a similar one in the Calama Basin, and regional structural data suggests that localized extension played an important role within a tectonic environment dominated by margin‐perpendicular compression and margin‐parallel strike‐slip deformation. Seismic data substantiate the surface interpretation that much of the Cordillera de la Sal ridge resulted from diapiric flow of the Paciencia Group. Diapiric flow initiated during the late early Miocene or middle Miocene, associated with a deep reverse fault.

S U M M A R YIn the summer of 1998, a series of multichannel, deep seismic reflection tests were conducted in central Tibet around 89 • E as part of the third phase of Project INDEPTH, a multidisciplinary study of the structure of the core of the Tibetan Plateau. Short seismic reflection sections from four locations spanning the Jurassic Banggong-Nujiang Suture show several features: thin (<2 km), sedimentary cover sequences; an unreflective upper crust down to approximately 25 km depth; strongly reflective lower crust down to 65 km depth (22 s traveltime) and a distinct change in seismic character from layered reflectivity to unreflective that we interpret as marking the reflection Moho. These profiles are unlike those in parts of the Yadong-Gulu Rift to the south where few deep reflections exist and reflection profiles are dominated by highamplitude reflection bright-spots at 6 s which have been interpreted as fluid bodies, either water or magma. Analyses of seismic amplitude decay on individual shot records confirm sourcegenerated energy at traveltimes beyond 22 s, thus indicating that the change in reflection character at the Moho is not the result of a loss of signal penetration. The depths to the top and bottom of the lower-crustal reflectivity match both a mid-crustal velocity increase and the Moho determined for this area from refraction profiling. Lower-crustal reflectivity is consistent with current ductile deformation as suggested by models for middle and lower-crustal flow in Tibet. However, Cretaceous-age magmatic intrusions may explain at least part of the observed reflectivity.

On 5 May 2014, a Mw 6.2 strike‐slip earthquake occurred in the Mae Lao region of Chiang Rai province in Thailand. This earthquake took place in a region of known faults and caused substantial damage and injuries, although the region had been previously identified as having a relatively low earthquake hazard. Detailed field reconnaissance and deployment of a dense, temporary, network of broadband seismometers allowed details of the damage and its relationship to seismicity to be analyzed. The aftershock sequence associated with this main shock occurs on two well‐defined trends, reflecting the two potential fault planes in earthquake mechanisms for the main shock and the majority of the aftershocks. The damage area was relatively large for an event of this magnitude, but building damage was largely limited to the primary rupture region, while liquefaction and other ground failure are spatially associated with the rupture area and along regional rivers. Stress modeling, combined with the time series and pattern of aftershock activity, leads us to propose that slip near the northern termination of the main shock rupture continued slightly onto a conjugate fault, helping to trigger the distinct pattern of two discrete, conjugate trends of aftershock activity that mirror the kinematics of the main shock fault mechanism.