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Abstract Interseismic coupling maps and, especially, estimates of the location of the fully coupled (locked) zone relative to the trench, coastline, and slow slip events are crucial for determining megathrust earthquake hazard at subduction zones. We present an interseismic coupling inversion that estimates the locations of the upper and lower boundaries of the locked zone, the lower boundary of the deep transition zone, and downdip gradient of creep rate in the transition from locked to freely creeping in the downdip transition zone. We show that the locked zone at Cascadia is west of the coastline and 10 km updip of the slow slip zone along much of the margin, widest (25–125 km, extending to ∼19 km depth) in northern Cascadia, narrowest (0–70 km) in central Cascadia, with moment accumulation rate equivalent to a M_w8.71 and M_w8.85 earthquake for 300‐ and 500‐year earthquake cycles. We find a steep gradient in creep immediately below the locked zone, indicative of propagating creep, along the entire margin. At Nankai, we find three distinct zones of locking (offshore Shikoku, offshore southeast Kii peninsula, and offshore Shima peninsula) with a total moment accumulation rate equivalent to a M_w8.70 earthquake for a 150‐year earthquake cycle. The bottom of the locked zone is nearly under the coastline for all three locked regions at Nankai and is positioned 0–5 km updip of the slow slip zone. In contrast with Cascadia, creep rate gradients below the locked zone at Nankai are generally gradual, consistent with stationary locking. 

Creating self-sustaining wireless sensor networks to power the Internet of Things requires universal energy harvesting systems. MEMS energy harvesters are in particular demand as they can be batch fabricated to meet the large supply demands. However, currently silicon MEMS kinetic energy harvesters are fabricated with a narrow bandwidth of 1–2 Hz, so each application requires a custom designed device which limits the advantages of batch fabrication. This paper investigates the development of a passive tuning MEMS vibration energy harvesting method that is based on distributing the load to various locations along the proof mass using a liquid load. A 3D printed proof mass with an array of cavities was developed, where each cavity could be filled with liquid to alter the resonant frequency as desired. Cavities were filled with silicone oil to validate the concept. The results illustrate tuning of the frequency with a resolution of < 1 Hz and a range of approximately 50 Hz. This method represents a passive tuning method as no power is required and the tuning can be accomplished during manufacturing so that one single universal energy harvester could be made and then tuned to meet the end user’s frequency specification. 

Microelectromechanical Systems (MEMS) energy harvesters have been extensively investigated over the past decade, but increasing power density and long-term reliability under high acceleration and low frequency are still major concerns. This study focused on the development of a low-frequency lead zirconate titanate (PZT) based energy harvester capable of operating at high acceleration >4 g with high power density performance. This study investigates the performance effects of altering the electrode configuration and poling configuration to maximize power density. The study investigated using four different types of electrode configuration consisting of long and short interdigitated electrodes (IDE) to operate in d 33 mode, and traditional parallel plate configuration to operate in d 31 mode. The results were numerically and experimentally validated. The results illustrate that the d 33 mode configuration was able to generate >3200 μW mm -3 with good reliability of up to 4 g. 

Abstract The paper presents the results of an investigation of a possibility for energy harvesting from a flexible material such as an ionic polymer–metal composite (IPMC) placed in a steady flow of air characteristic of conditions typical to a densely urbanized area. As electro-active devices require dynamic loading to produce current, their response is usually evaluated in unsteady and turbulent flows, where an electro-active polymer follows the movement of the medium surrounding the device. In our study, we examine the flow conditions at which flutter sets the IPMC strip in motion. Although flutter is often perceived as an unfavorable phenomenon for aerodynamic applications and civil structures, it may be beneficial for harvesting wind energy. Of particular interest is that this phenomenon may occur in a steady flow, which potentially expands the range of favorable flow conditions for energy harvesting. In the paper, the air speed at which flutter occurs and the speed range at which flutter is sustained are provided along with the estimated amount of power produced in an IPMC sample of specified dimensions.