Project report and algorithms for optimizing acquisition layout and frequency

D2.7. Project report and algorithms for optimizing acquisition layout and frequency. We evaluate the capability of 3D finite difference codes to model Distributed Acoustic Sensors (DAS) at reservoir scale for monitoring of CO2 sequestration. This work builds on previous DigiMon deliverables: 1.3 - DAS synthetic dataset (Baird et al, 2020b) and 2.1 - Framework for forward modelling of the DigiMon data (Vandeweijer et al, 2021). The goals of this work include 1) evaluation of the computational load and trade-offs needed to model Distributed Acoustic Sensing (DAS) signals from a 3D (~14x14x3 km) model of a CO2 sequestration reservoir; 2) sensitivity of various DAS deployment models (borehole versus surface); 3) comparison of DAS (linear and helical) with respect to geophones for both vertical and surface installations; and 4) measurements of possible induced seismicity with DAS

震源と地震動における地表断層地震と地中断層地震との相違

In previous work, we have shown that the ground motions from crustal earthquakes that break the ground surface are weaker than the ground motions from buried faulting crustal earthquakes. In this paper, we describe differences in kinematic and dynamic source parameters that may give rise to these differences in ground motion levels. From kinematic rupture models, we show that the slip velocity of surface faulting earthquakes is less that the slip velocity of buried faulting earthquakes. From dynamic rupture models, we infer that rupture in the shallow part of fault (upper few km) is controlled by velocity strengthening, with larger slip weakening distance Dc, larger fracture energy, larger energy absorption from the crack tip, lower rupture velocity, and lower slip velocity than at greater depths on the fault. Dynamic rupture modeling using these properties results in lower ground motions for surface faulting than for buried faulting events, consistent with the observations

Data from lab-scale experiments of fibre optic vibration measurement

Understanding the exact nature of the coupling of the optical fiber in response to seismic waves in a variety of settings is key to quantitative interpretation and modelling of seismic data recorded by Distributed Acoustic Sensors (DAS). While field experiments are very useful for gaining understanding their interpretation is complicated by variations in the conditions along the fibre, such how “straight” the fibre is at a given location, and the properties of the surrounding material. Lab-scale experiment can be useful for investigating specific parameters, since they allow for precise control over the local conditions over short lengths of fibre. This activity works towards the establishment of a lab-scale test bed for characterizing fibre optic response to seismic disturbancesData from lab-scale experiments of fibre optic vibration measurementpublishedVersio

2次元および3次元不均質構造における波動伝播のモデル化および強震動予測へのその応用

京都大学0048新制・課程博士博士(理学)甲第6680号理博第1815号新制||理||989(附属図書館)16102UT51-97-H64京都大学大学院理学研究科地球惑星科学専攻(主査)教授 入倉 孝次郎, 教授 安藤 雅孝, 助教授 赤松 純平学位規則第4条第1項該当Doctor of ScienceKyoto UniversityDA

Differences in Earthquake Source and Ground Motion Characteristics between Surface and Buried Crustal Earthquakes

In previous work, we have shown that the ground motions from crustal earthquakes that break the ground surface are weaker than the ground motions from buried faulting crustal earthquakes. In this paper, we describe differences in kinematic and dynamic source parameters that may give rise to these differences in ground motion levels. From kinematic rupture models, we show that the slip velocity of surface faulting earthquakes is less that the slip velocity of buried faulting earthquakes. From dynamic rupture models, we infer that rupture in the shallow part of fault (upper few km) is controlled by velocity strengthening, with larger slip weakening distance Dc, larger fracture energy, larger energy absorption from the crack tip, lower rupture velocity, and lower slip velocity than at greater depths on the fault. Dynamic rupture modeling using these properties results in lower ground motions for surface faulting than for buried faulting events, consistent with the observations

Exploring spatial coherence between earthquake source parameters

We explore the spatial coherence between earthquake source parameters by analyzing kinematic rupture models of two large strike-slip events, that is, the 1999 Izmit, Turkey, and the 1992 Landers, California, earthquakes. We investigate the coherence not only at zero offset but also at nonzero offset distances on the fault. The analysis shows that earthquake slip has a significant level of correlation with temporal source parameters such as rupture velocity, peak slip rate, and slip duration (rise time). We also show that many interesting features of earthquake source characteristics, such as directional effects of earthquake rupture, can be captured by this type of spatial coherence analysis. A coherence analysis therefore may have potential for understanding earthquake source characteristics and for generating realistic kinematic rupture models that capture the essential physics of the rupture process for strong ground motion prediction.8 page(s