Q estimation based on the logarithmic spectral area double difference

The Q factor is an essential parameter describing the characteristics of medium absorption within a material during wave propagation. When a seismic wave propagates within the attenuating media, its amplitude decreases and frequency band narrows, resulting in a variation in its logarithmic spectral area. Based on these effects, we calculate the logarithmic spectral area difference (LSAD) before and after attenuation and set a division point to divide the LSAD into two parts. We then compute the difference between the two LSADs to derive a new Q-estimation formula based on computation of the logarithmic spectral area double difference (LSADD). To improve the noise robustness of the Q estimation, we select multiple different division points to calculate the Q factors and consider their average value as our final estimate. We then compare and analyze the noise robustness and bandwidth sensitivity of our technique with other commonly used methods. These results demonstrate that our approach is the most accurate and robust, and least sensitive to the frequency band when processing noisy synthetic seismograms. Finally, we apply our methodology to field vertical seismic profile (VSP) and seismic reflection data, further illustrating the effectiveness of this method to estimate the Q factor.

A snapshot of the earliest stages of normal fault development

Despite decades of study, models for the growth of normal faults lack a temporal framework within which to understand how these structures accumulate displacement and lengthen through time. Here, we use borehole and high-quality 3D seismic reflection data from offshore Norway to quantify the lateral (0.2-1.8 mmyr-1) and vertical (0.004-0.02 mmyr-1) propagation rates (averaged over 12-44 Myr) for several long (up to 43 km), moderate displacement (up to 225 m) layer-bound faults that we argue provide a unique, essentially ‘fossilised’ snapshot of the earliest stage of fault growth. We show that lateral propagation rates are 90 times faster than displacement rates during the initial 25% of their lifespan suggesting that these faults lengthened much more rapidly than they accrued displacement. Although these faults have slow displacement rates compared with data compiled from 30 previous studies, they have comparable lateral propagation rates. This suggests that the unusual lateral propagation to displacement rate ratio is likely due to fault maturity, which highlights a need to document both displacement and lateral propagation rates to further our understanding of how faults evolve across various temporal and spatial scales.

How do tectonics influence the initiation and evolution of submarine canyons A case study from the Otway Basin, SE Australia

The architecture of canyon-fills can provide a valuable record of the link between tectonics, sedimentation, and depositional processes in submarine settings. We integrate 3D and 2D seismic reflection data to investigate the dominant tectonics and sedimentary processes involved in the formation of two deeply buried (c. 500 m below seafloor), and large (c. 3-6 km wide, >35 km long) Late Miocene submarine canyons. We found the plate tectonic-scale events (i.e. continental breakup and shortening) have a first-order influence on the submarine canyon initiation and evolution. Initially, the Late Cretaceous (c. 65 Ma) separation of Australia and Antarctica resulted in extensional fault systems, which then formed stair-shaped paleo-seabed. This inherited seabed topography allowed gravity-driven processes (i.e. turbidity currents and mass-transport complexes) to occur. Subsequently, the Late Miocene (c. 5 Ma) collision of Australia and Eurasia, and the resulting uplift and exhumation, have resulted in a prominent unconformity surface that coincides with the base of the canyons. We suggest that the Late Miocene intensive tectonics and associated seismicity have resulted in instability in the upper slope that consequently gave rise to emplacement of MTCs, initiating the canyons formation. Therefore, we indicate that regional tectonics play a key role in the initiation and development of submarine canyons.

Reservoir Architecture Modeling at Sub-Seismic Scale for a Depleted Carbonate Reef Reservoir for CO2 Storage in Sarawak Basin, Offshore Malaysia

It is still a challenge to build a numerical static reservoir model, based on limited data, to characterize reservoir architecture that corresponds to the geological concept models. The numerical static reef reservoir model has been evolving from the oversimplified tank-like models, simple multi-layer models to the complex multi-layer models that are more realistic representations of complex reservoirs. A simple multi-layer model for the reef reservoir with proportional layering scheme was applied in the CO2 Storage Development Plan (SDP) study, as the most-likely scenario to match the geological complexity. Model refinement can be conducted during CO2 injection phase with Measurement, Monitoring and Verification (MMV) technologies for CO2 plume distribution tracking. The selected reservoir is a Middle to Late Miocene carbonate reef complex, with three phases of reef growth: 1) basal transgressive phase, 2) lower buildup phase, and 3) upper buildup phase. Three chronostratigraphic surfaces were identified on 3D seismic reflection data as the zone boundaries, which were then divided into sub-zones and layers. Four layering methods were compared, which are ‘proportional’, ’follow top’, ‘follow base’ and ‘follow top with reference surface’. The proportional layering method was selected for the base case of the 3D static reservoir model and the others were used in the uncertainty analysis. Based on the results of uncertainty and risk assessment, a risk mitigation for CO2 injection operation were modeled and three CO2 injection well locations were optimized. The reservoir architecture model would be updated and refined by the difference between the modeled CO2 plume patterns and The MMV results in the future.

Stratigraphic and tectonic framework of Late Cretaceous and Paleogene strata of southern Aotea Basin, northwest New Zealand

<p>Seismic reflection data reveal thick sediment sequences of Late Cretaceous to Paleogene age in the region northwest of Taranaki Basin. A new stratigraphic framework for latest Cretaceous and Paleogene strata is created based on stacking patterns and stratal termination relationships of seismic reflectors. Sequence-bounding reflectors are tied to petroleum exploration wells, including recently-drilled Romney-1, to assign age and paleoenvironment interpretation. I identify the following sequences: (1) a late Haumurian to Teurian (68 – 56 Ma) aggradational shelf sequence, with at least two regressional events linked to eustatic sea-level falls; (2) a diachronous deepening of the basin that progressed from north to south during the late Waipawan to Heretaungan (53 – 46 Ma); (3) small-scale volcanism at the southern boundary with Taranaki Basin is contemporaneous with this deepening; (4) a prograding delta on Challenger Plateau during the Porangan to Runangan (46 – 35 Ma) that is evidence for tectonic uplift of the basin margins; and (5) an onlapping sequence from latest Runangan to present (35 – 0 Ma) that indicates Challenger Plateau subsided 1,300 m. A revised set of paleogeography maps and generalised stratigraphic chart summarise these observations. The Eocene phase (52-46 Ma) of tectonic subsidence and diffuse volcanism is one of the earliest signs of tectonic activity associated with development of the Cenozoic plate boundary through New Zealand. Petroleum system analysis reveals that southern Aotea Basin is prospective for petroleum exploration, with 3 plays identified in the Late Haumurian to Teurian (79 – 56 Ma) strata, in spite of Romney-1 proving unsuccessful.</p>

A seismic stratigraphic model for understanding the sedimentary and tectonic evolution of Solander Trough, offshore Fiordland, New Zealand

<p>Solander Trough is located offshore and south of Fiordland, New Zealand, adjacent to the geologically young Pacific-Australian plate boundary. Petroleum industry exploration was restricted to the near-shore. This thesis presents the first stratigraphic analysis of Solander Trough south of ~46.5°S, using 2D seismic reflection data acquired and processed onboard the R/V Marcus G. Langseth in 2018 (voyage MGL1803). The only pre-existing high-quality line, which was acquired onboard the R/V Maurice Ewing during voyage EW9601a in 1996, was reprocessed. The study area is divided into northern and southern sub-basins by Tauru High. Four megasequences and eight sequences are identified in the northern sub-basin (SLN). In the southern sub-basin (SLS), three megasequences and seven sequences are mapped. Biostratigraphy from the Parara-1 exploration well enabled age determination in the northern sub-basin. High resolution (~10 m) swath bathymetry data collected along seismic reflection lines provide insight into modern sedimentary processes. Solander Trough formed in the Eocene, but most sediment is young (<~15 Ma). Puysegur Ridge formed in the Miocene during subduction initiation and now shelters Solander Trough from the Antarctic Circumpolar Current, which affects depositional architecture. The oldest megasequences, SLN1 and SLS1, relate to normal-faulted basement with irregular relief. An increase in sediment supply from the north created megasquence SLN2, but it is thin and not recognised in the southern sub-basin. Megasequence SLN3 signals reverse reactivation on the Parara Anticline and Tauru High; its equivalent (SLS2) marks the first sediments rapidly deposited in southern Solander Trough, and is also linked in the south to initial growth of Puysegur Ridge. SLN4 is a product of Pliocene-Quaternary reverse reactivation of Solander Anticline, and its correlative, SLS3 in the southern sub-basin, is related to folding and widening of the eastern margin of Puysegur Ridge.</p>

Stratigraphic and tectonic framework of Late Cretaceous and Paleogene strata of southern Aotea Basin, northwest New Zealand

<p>Seismic reflection data reveal thick sediment sequences of Late Cretaceous to Paleogene age in the region northwest of Taranaki Basin. A new stratigraphic framework for latest Cretaceous and Paleogene strata is created based on stacking patterns and stratal termination relationships of seismic reflectors. Sequence-bounding reflectors are tied to petroleum exploration wells, including recently-drilled Romney-1, to assign age and paleoenvironment interpretation. I identify the following sequences: (1) a late Haumurian to Teurian (68 – 56 Ma) aggradational shelf sequence, with at least two regressional events linked to eustatic sea-level falls; (2) a diachronous deepening of the basin that progressed from north to south during the late Waipawan to Heretaungan (53 – 46 Ma); (3) small-scale volcanism at the southern boundary with Taranaki Basin is contemporaneous with this deepening; (4) a prograding delta on Challenger Plateau during the Porangan to Runangan (46 – 35 Ma) that is evidence for tectonic uplift of the basin margins; and (5) an onlapping sequence from latest Runangan to present (35 – 0 Ma) that indicates Challenger Plateau subsided 1,300 m. A revised set of paleogeography maps and generalised stratigraphic chart summarise these observations. The Eocene phase (52-46 Ma) of tectonic subsidence and diffuse volcanism is one of the earliest signs of tectonic activity associated with development of the Cenozoic plate boundary through New Zealand. Petroleum system analysis reveals that southern Aotea Basin is prospective for petroleum exploration, with 3 plays identified in the Late Haumurian to Teurian (79 – 56 Ma) strata, in spite of Romney-1 proving unsuccessful.</p>

A seismic stratigraphic model for understanding the sedimentary and tectonic evolution of Solander Trough, offshore Fiordland, New Zealand

<p>Solander Trough is located offshore and south of Fiordland, New Zealand, adjacent to the geologically young Pacific-Australian plate boundary. Petroleum industry exploration was restricted to the near-shore. This thesis presents the first stratigraphic analysis of Solander Trough south of ~46.5°S, using 2D seismic reflection data acquired and processed onboard the R/V Marcus G. Langseth in 2018 (voyage MGL1803). The only pre-existing high-quality line, which was acquired onboard the R/V Maurice Ewing during voyage EW9601a in 1996, was reprocessed. The study area is divided into northern and southern sub-basins by Tauru High. Four megasequences and eight sequences are identified in the northern sub-basin (SLN). In the southern sub-basin (SLS), three megasequences and seven sequences are mapped. Biostratigraphy from the Parara-1 exploration well enabled age determination in the northern sub-basin. High resolution (~10 m) swath bathymetry data collected along seismic reflection lines provide insight into modern sedimentary processes. Solander Trough formed in the Eocene, but most sediment is young (<~15 Ma). Puysegur Ridge formed in the Miocene during subduction initiation and now shelters Solander Trough from the Antarctic Circumpolar Current, which affects depositional architecture. The oldest megasequences, SLN1 and SLS1, relate to normal-faulted basement with irregular relief. An increase in sediment supply from the north created megasquence SLN2, but it is thin and not recognised in the southern sub-basin. Megasequence SLN3 signals reverse reactivation on the Parara Anticline and Tauru High; its equivalent (SLS2) marks the first sediments rapidly deposited in southern Solander Trough, and is also linked in the south to initial growth of Puysegur Ridge. SLN4 is a product of Pliocene-Quaternary reverse reactivation of Solander Anticline, and its correlative, SLS3 in the southern sub-basin, is related to folding and widening of the eastern margin of Puysegur Ridge.</p>

Flexural strike-slip basins

Strike-slip faults are classically associated with pull-apart basins where continental crust is thinned between two laterally offset fault segments. We propose a subsidence mechanism to explain the formation of a new type of basin where no substantial segment offset or syn-strike-slip thinning is observed. Such “flexural strike-slip basins” form due to a sediment load creating accommodation space by bending the lithosphere. We use a two-way coupling between the geodynamic code ASPECT and surface-processes code FastScape to show that flexural strike-slip basins emerge if sediment is deposited on thin lithosphere close to a strike-slip fault. These conditions were met at the Andaman Basin Central fault (Andaman Sea, Indian Ocean), where seismic reflection data provide evidence of a laterally extensive flexural basin with a depocenter located parallel to the strike-slip fault trace.