Water seepage in concrete threatens the safety of marine constructions and reduces the durability of concrete structures. This note presents a smart aggregate-based monitoring method to monitor the travel time evolution of a harmonic stress wave during the water infiltrating process in concrete structures. An experimental investigation, in which two plain concrete columns were examined under different water infiltration cases, verified the validity of the proposed monitoring method. The test results show that the travel time of the harmonic stress wave is sensitive to the development of water seepage in concrete and decreases with increasing water seepage depth. The proposed active monitoring method provides an innovative approach to monitor water seepage in concrete structures.

On 6 February 2023, two large earthquakes with magnitude 7.8 and 7.6 rocked south-central Türkiye and northwestern Syria. At the time of writing, the death toll exceeded 50,000 in Türkiye and 7200 in Syria. The epicenter of the first mainshock was located ∼15 km east of the east Anatolian fault (EAF), the second large earthquake (9 hr later) initiated ∼90 km to the north on the east–west-trending Sürgü fault. Aftershocks delineate fault lengths of ∼350 and ∼170 km, respectively. Using satellite and seismic data for first-order analyses of surface-fault offsets, space–time rupture evolution, and recorded ground motions, our study sheds light on the reasons for the extensive destruction. The first event ruptured the EAF bilaterally, lasted for ∼80 s, and created surface fault offsets of over 6 m. The second event also ruptured bilaterally with a duration of ∼35 s and more than 7 m surface offsets. Horizontal ground accelerations reached locally up to 2g in the first mainshock; severe and widespread shaking occurred in the Hatay-Antakia area with values near 0.5g. Both earthquakes are characterized by directivity effects and abrupt rupture cessation generating stopping phases that contributed to strong seismic radiation. Shaking was further aggravated locally by site-amplification effects.

Jet propulsion is the main method of locomotion developed by cephalopods to swim through water, either for hunting or escaping from predators. Under this inspiration, diverse underwater robots utilizing jet propulsion-based locomotion are studied. This article presents a cephalopod-inspired robot based on a dielectric elastomer actuator, utilizing jet-propulsion actuation. The actuator is designed and optimized under the guidance of a corresponding electromechanical model. Then, the flow field characteristics of the synthetic jet actuator are simulated and analyzed. Equipped with the actuator, the bioinspired robot can locomote either with a speed of 0.66 body length per second on the surface of the water by jetting air or with a speed of 0.43 body length per second while almost completely submerged underwater by jetting water. The jet actuator presents even more environmental adaptability, which powers dual swimming locomotion by jetting two flow media, and can potentially be applied to the design of underwater robots.

The overwhelming observational difficulties and the complexity of earthquake physics have rendered seismic hazard assessment largely empirical. Despite increasingly high-quality geodetic, seismic, and field observations, data-driven earthquake imaging yields stark differences and physics-based models explaining all observed dynamic complexities are elusive. Here we present data-assimilated 3D dynamic rupture models which untwine California's biggest earthquakes in more than 20 years: the moment magnitude (M w ) 6.4 Searles Valley and M w 7.1 Ridgecrest, California, sequence breaking multiple segments of the same fault system. Our models use supercomputing to find the link between the two large earthquakes. We unify the uniquely high-quality strong-motion and teleseismic, field mapping, high-rate GNSS, and space geodetic foreshock and mainshock datasets with earthquake physics. We find that the regional structure, the ambient long-and short-term stress, as well as the dynamic and static fault system interactions, are conjointly crucial to understand the dynamics and delays of the sequence.Dynamic rupture of a statically strong yet dynamically weak fault system is driven by overpressurized fluids and low dynamic friction in our models. The observed earthquake complexity results from static and dynamic stress changes acting across a non-vertical quasi-orthogonal conjugate fault structure. We demonstrate that joint physics-based and data-driven illumination of the mechanics of complex fault systems and earthquake sequences is possible when reconciling dense earthquake recordings, 3D regional structure and stress models. We foresee that physics-based interpretation of big observational data-sets characterizing complex nonlinear systems will have a transformative impact on future geohazard mitigation.