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Presentation Mode : All
Conference Day : 02/08/2021
Time Slot : AM2 11:00 - 13:00
Sections : SE - Solid Earth Sciences










Solid Earth Sciences | Mon-02 Aug




SE11-A016
A New Range of Seismic Instruments to Meet the Wide Range of Applications in Southeast and East Asia: the Guralp Smart Range

Ella PRICE#+
Guralp Systems Ltd, United Kingdom


The regions of Southeast and East Asia both present large variation in geological history, active tectonics and seismic hazards. This calls for a flexible range of instruments to research, monitor and protect against seismicity in an equally varied range of environments. Güralp’s new generation of seismic instruments focus on the core belief that instruments should be simple to configure, install and operate while maintaining large degrees of flexibility to suit multiple environments. The seismic community is increasingly calling for low-logistics installation in remote areas with minimal maintenance required.Southeast and East Asia contain a complex range of tectonic environments including many harsh or otherwise generally inaccessible environments. The Güralp smart range of instruments increases the capability of operators to access these areas through compact size, ultra-low-power and the ability to operate at any angle without levelling. This dramatically increases data quality, especially during rainy seasons when installations are most likely to tilt due to water saturation. The smart range of instruments revolves around the Minimus digitiser, which is used with all analogue instruments, as well as being incorporated into digital strong-motion accelerometers, broadband seismometers, ocean-bottom and borehole systems. This opens up a broad range of applications from structural health monitoring, through to earthquake and tsunami warning systems, all of which are persistent hazards in the region.

SE11-A015
3D Ground Motion Predictions of Scenario Earthquakes in the Southeastern Korean Peninsula

Jaeseok LEE1+, Jung-Hun SONG1, Junkee RHIE1, Seok Goo SONG2, Seongryong KIM3#
1Seoul National University, Korea, South, 2Korea Institute of Geoscience and Mineral Resources, Korea, South, 3Korea University, Korea, South


Accurate and practical ground motion predictions for potential large earthquakes are crucial for seismic hazard analysis of areas where instrumental data are lacking. Studies on historical earthquake records of the Korean peninsula have suggested future possibilities of damaging earthquake ruptures in the southeastern region, yet the classical ground motion prediction methods in applications bear evident limitations in considering the physical rupture process and its effects on ground motion in complex velocity structures. In this study, we perform ground motion simulations based on rigorous physics through pseudo-dynamic source modeling and wave propagation simulations in a three-dimensional velocity structure. Ensembles of earthquake scenarios were generated by emulating the 1-point and 2-point statistics of earthquake source parameters derived from a series of dynamic rupture models. The distributions of the simulated peak ground velocities were inspected and compared with the observations of the 2016 MW 5.4 Gyeongju earthquake in the Korean Peninsula to test the reliability of our approach. Effects of surface-wave radiation, rupture directivity, and 3-D wave propagations are recognized in the spatial distribution of simulated peak ground velocities as observed in dense seismic networks. We extend the established approach to scenario earthquakes of MW 6.0, 6.5, and 7.0 at the same location to provide a potential distribution of ground motion intensities. The simulation results suggest large potential ground motions with high variabilities in the low-velocity regions of the southeastern Korean Peninsula. This research demonstrates the application prospects of physics-based source and wave propagation simulations for statistical ground motion predictions in regions of low-to-moderate seismicity.

SE11-A019
Ongoing Postseismic Deformation of the Australian Continent from Far-field Plate Boundary Earthquakes

Matt KING#+, Anna RIDDELL, Christopher WATSON
University of Tasmania, Australia


Vertical deformation of Australia due to earthquakes has previously been considered as negligible or undetectable using modern geodetic techniques. We investigate the magnitude, duration and extent of coseismic and postseismic deformation across Australia using GPS time series and compare these with elastic and viscoelastic predictive model outputs. We observe and model surface deformation in Australia caused by far-field plate boundary events, including: 2004 Mw 8.1 Macquarie Ridge, 2004 Mw 9.3 Sumatra-Anderman, 2005 Mw 8.6 in northern Sumatra, the 2007 series of Mw 8.5 and 7.9 in southern Sumatra, two events in 2012 of Mw 8.6 and 8.2 in northern Sumatra, and the 2009 Mw 7.8 south of New Zealand. In the vertical component, we find coseismic offsets of up to 3 mm more than 5000 km from the earthquake event, and postseismic signals reaching several mm/yr sustained over several years. In particular, the Sumatran sequence produces observed subsidence in north-western Australia of up to 4 mm/yr over 2004.9-2010.0 where predictions based on one-dimensional viscoelastic Earth models replicate the subsidence but underpredict the vertical rate by at least a factor of two. We suggest that this is due to limitations in using viscoelastic deformation models with a 1D (radially varying) Earth model, whereas the Earth rheological structure between the offshore earthquakes and continental Australia is complex. A 3D laterally and radially varying model is needed to test these ideas. Across all earthquakes, the predictive models often fit one or two coordinate components of the observations, but rarely all three. Unmodeled lateral rheological structure likely contributes to this given the difference between the oceanic location of the earthquakes and the Australian continental setting of the GPS sites. The magnitude and spatial extent of these coseismic and postseismic deformations warrant their consideration in future updates of the geodetic terrestrial reference frame.

SE11-A024
Study of Fault Zone and Basin Structure of 2019 Mw5.5 Ye-U Earthquake Sequence Beneath Central Myanmar Basin

Win Shwe Sin OO1#+, Wardah FADIL1, Karen LYTHGOE1, Yukuan CHEN1, Dannie HIDAYAT1, Lin Thu AUNG1, Wan Lin HU1, Hongyu ZENG1, Phyo Maung MAUNG2, Shengji WEI1, Eimhonnathar MYO3, Win Min THAN4, Pyae Phyo HAN5
1Nanyang Technological University, Singapore, 2Nanyang Technological University (NTU), Singapore, 3National Taiwan University, Taiwan, 4Mandalay University, Myanmar, 5Monywa University, Myanmar


Accurate and precise location of earthquake sequence is critical to better understand seismotectonics, such as better delineation fault geometry and understanding of the rupture of the earthquakes. However, nearfield seismic observations are usually rare for such study. Here we study a unique dense nodal array data acquired by the deployment after the 31/08/2019 Mw5.5 crustal earthquake that is located ~50km to the west of Sagaing fault near Mandalay beneath ShweBo Central Myanmar Basin (CMB). The network, composed of 20 nodal stations with station spacing of ~5km, was deployed ~ 2 weeks after the mainshock and continuously recording for ~ 40 days. High quality waveforms containing clear P and S phase arrivals, and an interesting P-to-S phase converted at the basement of CMB were recorded for aftershocks. We applied a machine learning based automatic phase detection software (Earthquake-Transformer) to the dataset and detected 1143 events that were recorded by at least 3 stations. Double difference relocation of these aftershocks reveals a near E-W trending fault with a dimension of ~10km along strike and located between 7 to 12 km in depth. The strike of aftershock lineation is highly consistent with the focal mechanism derived from regional waveform inversion, indicating a left lateral strike-slip fault beneath CMB. Mainshock epicenter refined by a path calibration technique is located to the western edge of the seismicity, suggesting an eastward rupture directivity of the mainshock. Taking advantage of the P-basin-S converted phase at the basement of CMB, we constrained the thickness of the basin to be 5 ± 0.7 km. Strong strength of the P-basin-S phase requires sharp velocity change between the basin and bedrock. We interpret the earthquake sequence as a result of small block rotation that has been taking place beneath the CMB due to the convergence of India plate.