Insights into spatio-temporal slow slip events offshore the Boso Peninsula in central Japan during 2011-2019 using GPS data

Using Global Positioning System(GPS)coordinate time series,we detect three transient slow slip events(SSEs)offshore the Boso Peninsula in central Japan during 2011-2019.To extract the tiny SSE signals obscured by the significant post-seismic deformation after the 2011 MW9.0 Tohoku earthquake,we develop a new GPS coordinate time series processing software to obtain these SSE-induced deformations from highnoise GPS data.In addition,we apply the principal component analysis-based inversion method(PCAIM)to get the spatio-temporal slip distribution of the three SSEs.The spatio-temporal evolutions of these slips reveal that the nucleation styles are different.Compared to the 2011 and 2018 SSEs,the 2013-2014 SSE displays faster slip spatio-temporal variation,deeper slip,shorter slip duration,minor seismic moment,and lower maximum slip rate.The 2018 SSE exhibits the most significant seismic moment,the maximum slip,and the maximum slip rate of these three SSEs.The spatio-temporal variations of the 2011 SSE are the most complex,containing two acceleration and deceleration phases.The slip zone expanded along the eastern side of the Boso Peninsula in the acceleration phase and shrank back in the deceleration phase.Furthermore,the recurrence interval of SSEs spans from 2.2 to 4 years during 2011-2019,suggesting that the recurrence interval might become shorter and non-periodic due to the enormous earthquake.After the 2013-2014 SSE,the recurrence interval of the SSE gradually returns to normal.Thus,we can infer that the SSE may occur every 4-7 years after the 2018 SSE if there is no large earthquake.

Lightweight Direct Acyclic Graph Blockchain for Enhancing Resource-Constrained IoT Environment

Blockchain technology is regarded as the emergent security solution for many applications related to the Internet of Things(IoT).In concept,blockchain has a linear structure that grows with the number of transactions entered.This growth in size is the main obstacle to the blockchain,which makes it unsuitable for resource-constrained IoT environments.Moreover,conventional consensus algorithms such as PoW,PoS are very computationally heavy.This paper solves these problems by introducing a new lightweight blockchain structure and lightweight consensus algorithm.The Multi-Zone Direct Acyclic Graph(DAG)Blockchain(Multizone-DAG-Blockchain)framework is proposed for the fog-based IoT environment.In this context,fog computing technology is integrated with the IoT to offload IoT tasks to the fog nodes,thus preserving the energy consumption of the IoT devices.Both IoT and fog nodes are initially authenticated using a non-cloneable physical function-based validationmechanism(DPUF-VM)inwhichmultiple authentication certificates are verified in the blockchain.Each transaction is stored in a hash function in the blockchain using the lightweight CubeHash algorithm and signed by the Four-Q-Curve algorithm.In the cloud,sensitive data is stored as ciphertext.Fog nodes provide data security to avoid the energy consumption and complexity of IoT nodes.The fog node first performs a redundancy analysis using the Jaccard Similarity(JS)measure and sensitivity analysis using the Neutrosophic Neural Intelligent Network(N2IN)algorithm.A lightweight proof-of-authentication(PoAh)algorithm is presented and executed by the optimal consensus node selected by the bi-objective spiral optimization(BoSo)algorithm for transaction validation.The proposed work is modeled in Network Simulator 3.26(ns-3.26),and the performance is evaluated in terms of energy consumption,storage cost,response time,and throughput.