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Modelling Rapid Near Field Attenuation from Shallow Induced Earthquakes, Case Study: Preston New Road, UK

Session: Advances in Understanding Near-Field Ground Motions: Observation, Prediction and Application I

Type: Oral

Date: 4/22/2021

Presentation Time: 10:45 AM Pacific

Description: 

The significant growth of human-induced earthquakes in recent years has drawn public attention. Many attempts have been made to model seismic-induced ground motion, typically by implementing, and frequently adapting, pre-existing tectonic ground motion prediction equations (GMPEs). However, tectonic GMPEs are often unsuitable for adaptation to induced seismicity. In particular, they offer insufficient functional flexibility to fully adapt to the near-field shallow source scenarios typical of such events. For instance, rapid near field decay is often observed owing to travel paths that propagate predominantly through shallow sedimentary layers. Estimating attenuation behavior specific to shallow source events in the near field is therefore an important factor to consider in the development of GMPEs for induced seismicity applications. Here we investigate physical mechanisms of the difference between shallow induced and tectonic seismicity by directly modeling seismic attenuation of UK seismicity, with focus on the Preston New Road (PNR) shale gas induced seismicity sequences.

Measurements of seismic attenuation quality factor (Q) are non-unique and may differ depending on the method and the seismic windows used, particularly at high frequency. These inconsistencies may be due to methodological aspects or represent different physical processes. The PNR, UK dataset recorded between 2018-2019 with M_L< 3 at distances less than 25 km is utilised to model Q using two different approaches: (1) spectral fitting, and (2) coda envelope decay methods. The results from the spectral fitting method show three different frequency-independent Q models with respect to different parts of the recorded seismograms (S-wave, Q_S, coda wave, Q_C, and S+coda windows, Q_SC), while a frequency-dependent Q model was found from the coda envelope decay method (Q_Clt). These Q models of shallow induced seismicity tend to be smaller than the regional Q (Q_Lg(f) = 266 f^0.53) (Sargeant & Ottemöller, 2009).

Presenting Author: Pungky M. T. Suroyo

Student Presenter: Yes

Authors