The Central Italy earthquake sequence initiated on 24 August 2016 with a moment magnitude M 6.1 event, followed by two earthquakes ( M 5.9 and M 6.5) on 26 and 30 October, caused significant damage and loss of life in the town of Amatrice and other nearby villages and hamlets. The significance of this sequence led to a major international reconnaissance effort to thoroughly examine the effects of this disaster. Specifically, this paper presents evidences of strong local site effects (i.e., amplification of seismic waves because of stratigraphic and topographic effects that leads to damage concentration in certain areas). It also examines the damage patterns observed along the entire sequence of events in association with the spatial distribution of ground motion intensity with emphasis on the clearly distinct performance of reinforced concrete and masonry structures under multiple excitations. The paper concludes with a critical assessment of past retrofit measures efficiency and a series of lessons learned as per the behavior of structures to a sequence of strong earthquake events.

The Central Italy earthquake sequence nominally began on 24 August 2016 with a M 6.1 event on a normal fault that produced devastating effects in the town of Amatrice and several nearby villages and hamlets. A major international response was undertaken to record the effects of this disaster, including surface faulting, ground motions, landslides, and damage patterns to structures. This work targeted the development of high‐value case histories useful to future research. Subsequent events in October 2016 exacerbated the damage in previously affected areas and caused damage to new areas in the north, particularly the relatively large town of Norcia. Additional reconnaissance after a M 6.5 event on 30 October 2016 documented and mapped several large landslide features and increased damage states for structures in villages and hamlets throughout the region. This paper provides an overview of the reconnaissance activities undertaken to document and map these and other effects, and highlights valuable lessons learned regarding faulting and ground motions, engineering effects, and emergency response to this disaster.

As part of a broader effort to develop ground‐motion data resources for China in a manner consistent with Next Generation Attenuation projects, we develop a database of geotechnical soil profiles and shear‐wave velocity (⁠ $VS$⁠) logs for sites having ground‐motion accelerometers (this database is referred to as soil profile database [SPD]), and then use that data to develop site parameters. The site information is compiled for stations within the National Strong Motion Observation Network System (NSMONS) of China. This effort is focused on four provinces in western China (Yunnan, Sichuan, Gansu, and Xinjiang), which contribute 871 of 2023 NSMONS stations throughout China. Of the 871 sites, the SPD provides site information for 678 sites, or 78% of the total. To develop the SPD, geotechnical logs and/or $VS$ profiles are compiled for 637 sites. This information is derived from previously unpublished reports and is assembled here in a uniform format and partially disseminated (only approximate site locations are provided). The remaining 41 sites in the SPD have confirmed bedrock conditions at the ground surface. Site metadata and parameters are compiled into a database, included as a supplemental material to this article, that includes the depth to the first occurrence of 0.5 km/s shear‐wave velocity (⁠ $Z0.5$⁠), three time‐averaged shear‐wave velocity parameters (⁠ $VSe$⁠, $VS20$⁠, $VS30$⁠), and site classifications based on the Chinese building seismic design code and National Earthquake Hazards Reduction Program Provisions. For sites with $VS$ profiles that do not extend to 30 m, we present region‐specific recommendations for extrapolating time‐averaged velocities from the profile depth to 30 m. For sites with geotechnical logs but no profiles, we present procedures to estimate $VS$ profiles from which the earlier parameters can be derived.

The 2019 Ridgecrest earthquake sequence produced a 4 July $M$ 6.5 foreshock and a 5 July $M$ 7.1 mainshock, along with 23 events with magnitudes greater than 4.5 in the 24 hr period following the mainshock. The epicenters of the two principal events were located in the Indian Wells Valley, northwest of Searles Valley near the towns of Ridgecrest, Trona, and Argus. We describe observed liquefaction manifestations including sand boils, fissures, and lateral spreading features, as well as proximate non‐ground failure zones that resulted from the sequence. Expanding upon results initially presented in a report of the Geotechnical Extreme Events Reconnaissance Association, we synthesize results of field mapping, aerial imagery, and inferences of ground deformations from Synthetic Aperture Radar‐based damage proxy maps (DPMs). We document incidents of liquefaction, settlement, and lateral spreading in the Naval Air Weapons Station China Lake US military base and compare locations of these observations to pre‐ and postevent mapping of liquefaction hazards. We describe liquefaction and ground‐failure features in Trona and Argus, which produced lateral deformations and impacts on several single‐story masonry and wood frame buildings. Detailed maps showing zones with and without ground failure are provided for these towns, along with mapped ground deformations along transects. Finally, we describe incidents of massive liquefaction with related ground failures and proximate areas of similar geologic origin without ground failure in the Searles Lakebed. Observations in this region are consistent with surface change predicted by the DPM. In the same region, geospatial liquefaction hazard maps are effective at identifying broad percentages of land with liquefaction‐related damage. We anticipate that data presented in this article will be useful for future liquefaction susceptibility, triggering, and consequence studies being undertaken as part of the Next Generation Liquefaction project.

The 2016 Central Italy earthquake sequence caused numerous landslides over a large area in the Central Apennines. As a result, the Geotechnical Extreme Events Reconnaissance Association (GEER) organized post‐earthquake reconnaissance missions to collect perishable data. Given the challenging conditions following the earthquakes, the GEER team implemented a phased reconnaissance approach. This paper illustrates this approach and how it was used to document the largest and most impactful seismically induced landslides. This phased approach relied upon satellite‐based interferometric damage proxy maps, preliminary published reports of observed landslides, digital imaging from small unmanned aerial vehicles (UAVs), traditional manual observations, and terrestrial laser scanning. Data collected from the reconnoitered sites were used to develop orthophotos and meshed three‐dimensional digital surface models. These products can provide valuable information such as accurate measurements of landslide ground movements in complex topographic geometries or boulder runout distances from rock falls. The paper describes three significant landslide case histories developed and documented with the phased approach: Nera Valley, Village of Pescara del Tronto, and near the villages of Crognaleto and Cervaro.