Laboratory Measurements to Image Endobenthos and Bioturbation with a High-Frequency 3D Seismic Lander

The presented 3D seismic system operates three transducers (130 kHz) from a stationary lander and allows non-destructive imaging of small-scale objects within the top decimeters of silty sediments, covering a surface area of 0.2 m2. In laboratory experiments, samples such as shells, stones, and gummy worms of varied sizes (down to approx. 1 cm diameter) could be located in the 3D seismic cube to a depth of more than 20 cm and differentiated by a reflected amplitude intensity and spatial orientation. In addition, simulated bioturbation structures could be imaged. In a practical application, the system allows to determine the abundance of endobenthos and its dynamic in muddy deposits in-situ and thus identify the intensity of local bioturbation.

New Insights into the Lake Erie Fault System from the 2019 ML 4.0 Ohio Earthquake Sequence

We present a detailed analysis of the 10 June 2019 ML 4.0 Ohio earthquake sequence, which is the largest earthquake that struck Lake County, northeastern Ohio, since 1986. This sequence is well recorded by local seismic networks, which provides an unprecedented opportunity to understand the local seismotectonics. We utilize a waveform-based cross-correlation method to identify ∼12 times more events than reported by the Advanced National Seismic System (ANSS) Comprehensive Earthquake Catalog: the whole sequence started with several small earthquakes (ML 1–2) beginning 12 March 2019, and the last one occurred ∼1min immediately before the ML 4.0 mainshock; many previously unreported aftershocks (ML 0.3–2.2) are found, which were active for the first week after the mainshock; another major sequence with a 7 December 2019 ML 2.6 mainshock occurred and also started with a few smaller events beginning in mid-November and was followed by its own aftershocks. The relocated seismicity delineates a linear feature, orientation of which is consistent with the resolved focal plane that may correspond to the ruptured fault. Our results highlight that closer monitoring of local seismicity is crucial for understanding the seismotectonics and mitigating future seismic hazard around the southern Great Lakes.

Seismic performance of Greater Jakarta LRT with added lead rubber bearing using non-linear time history analysis

<p>In order to overcome stringent seismic requirement in the new Greater Jakarta Light Rail Transit Project, a breakthrough seismic system shall be chosen to obtain expected structural performance. This seismic system shall be designed to provide operational performance level after strong earthquake events. To achieve the criteria, seismic isolation system using Lead Rubber Bearings is chosen. With this isolation system, Greater Jakarta LRT has become the first seismically isolated infrastructure and apparently an infrastructure with the largest numbers of LRBs in one single project in Indonesia. More than 10.400 Pcs LRBs are used for the first phase of the construction and the numbers will be certainly increased in the next phase of the construction. To evaluate the structural performance, non-linear time history analysis is used. A total of 3 pair matched ground motions will be used as the input for the response history analysis. The ability of the lead rubber bearing to isolate and dissipate earthquake actions will determine its structural performance level. This will be represented by the nonlinear hysteretic curves obtained throughout the earthquake actions.</p>

Fine-scale velocity distribution revealed by datuming of very-high-resolution deep-towed seismic data: Example of a shallow-gas system from the western Black Sea

Very-high-resolution (VHR) marine seismic reflection helps to identify and characterize potential geohazards occurring in the upper part (300 m) of the subseafloor. Although the lateral and vertical resolutions achieved in shallow water depths ([Formula: see text]) using conventional surface-towed technology are adequate, these resolutions quickly deteriorate at greater water depths. The SYstème SIsmique de Fond (SYSIF), a multichannel deep-towed seismic system, has been designed to acquire VHR data (frequency bandwidth [220–1050 Hz] and vertical resolution of 0.6 m) at great water depths. However, the processing of deep-towed multichannel data is challenging because the source and the receivers are constantly moving with respect to each other according to the towing configuration. We have introduced a new workflow that allows the application of conventional processing algorithms to extended deep-towed seismic data sets. First, a relocation of the source and receivers is necessary to obtain a sufficiently accurate acquisition geometry. Variations along the profile in the depth of the deep-towed system result in a complex geometry in which the source and receiver depth vary separately and do not share the same acquisition datum. We have designed a dedicated datuming algorithm to shift the source and receivers to the same datum. Thus, the procedure allows the application of conventional processing algorithms to perform velocity analysis and depth imaging and therefore allows access to the full potential of the seismic system. We have successfully applied this methodology to deep-towed multichannel data from the western Black Sea. In particular, the derived velocity model highlights shallow gas charged anticline structures with unrivaled resolution.

Beyond Earthworm: Keeping the Promise

The founding of the Advanced National Seismic System (ANSS) vision was originally presented in U.S. Geological Survey Circular 1188 (U.S. Geological Survey [USGS], 1999), after many years of discussions and workshops, described in detail by Filson and Arabasz (2016). Much has been accomplished in the ensuing two decades. Disparate and sometimes divergent developments that had been previously explored at individual private and public universities were finally centralized with increased efficiency and coherency of effort. The stated mission of the ANSS is to “… provide accurate and timely data and information products for seismic events, including their effects on buildings and structures, employing modern monitoring methods and technologies.” In this article, an approach (xQuake) is proposed that does not interfere in any way with the mission of the National Earthquake Information Center and ANSS but instead restores much of the community focus and international collaboration that has been lost over the past two decades. xQuake uses an executable graph framework in a pipeline architecture; this framework can be seamlessly integrated into current ANSS quake monitoring systems. This new approach incorporates modern approaches to computer analytics, including multitopic Kafka exchange rings, cloud computing, a self-configuring phase associator, and machine learning. The xGraph system is free for noncommercial use, open source, hardware agnostic (Windows, Linux, Mac), with no requirement for commercial datastores.