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The 24 May 2024 landslide at Yambali in Papua New Guinea

EOS - Thu, 03/27/2025 - 07:57

The Landslide Blog is written by Dave Petley, who is widely recognized as a world leader in the study and management of landslides.

On 24 May 2024 at 2:56 am local time, a catastrophic landslide occurred close to Yambali in Enga Province, Papua New Guinea, at: [-5.382, 143.365]. I wrote about this rockslide at the time, and it generated considerable media interest. The site is hard to access, so details have been hard to track down.

There is a good new paper (Li et al. 2025) in the journal Landslides, sadly behind a paywall (but the contact details of the first author are in the link above), which provides an initial review of the event.

One of the reasons that this landslide attracted so much attention was the reported loss of life, which in some cases was up to 2,000 people. As I noted at the time, this was highly unlikely in a rural area. Li et al. (2025) have mapped the houses destroyed by the event (n=29), suggesting that the likely loss of life was in the region of 200.

Whilst it was spectacular, the landslide at Yambali was not huge – Li et al. (2025) have measured the runout distance as 520 m, with a maximum width of 140 m. The volume was about 500,000 m3. The failure occurred on a steep slope that is bisected by a fault, consisting of “relatively low-strength, highly weathered quartz sandstone and limestone”. The authors note that there were smaller failures on the slope before the main event, suggesting that this was a progressive event. No direct trigger has been identified, but the six months period before the failure occurred had unusually high levels of precipitation.

The international interest in this landslide has now ebbed away, leaving the local population to deal with the aftermath. The Planet image below, captured last week, shows the site:-

Planet image of the 24 May 2024 landslide near to Yambali in Papua New Guinea. Image copyright Planet, used with permission. Image dated 18 March 2025.

A new road has been constructed to bypass the site, presumably to reopen access to the mine. Unfortunately, this is likely to leave those living along the original alignment even more isolated than before.

Reference

Li, Z., Li, W., Xu, Q. et al. 2025. Brief report on the catastrophic landslide in Papua New Guinea on May 24, 2024. Landslides. https://doi.org/10.1007/s10346-025-02511-0

Planet Team 2025. Planet Application Program Interface: In Space for Life on Earth. San Francisco, CA. https://www.planet.com/

Return to The Landslide Blog homepage Text © 2023. The authors. CC BY-NC-ND 3.0
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Slow and progressive deformation of the Narlı pull-apart basin prior to the 2023 Mw7.8 kahramanmaraş, Turkey earthquake

Geophysical Journal International - Thu, 03/27/2025 - 00:00

SummaryThe ∼300km-long rupture of the February 6 2023 Kahramanmaraş earthquake began in the Narlı section of the Karasu trough, a pull-apart basin sandwiched and sheared between the two major strike-slip faults of the region, the East Anatolian Fault (EAF) on the west and the Dead Sea Fault (DSF) on the east. Rupture started where the northern segment of the DSF enters the Narlı Basin with Mw7.0 sub-event and propagated across the basin before making its junction with the EAF. In the seven months preceding the earthquake this basin was the seat of anomalous seismic activity. This activity occurred in bursts interweaved with periods of quiescence. It started near-concomitantly in two clusters located on the opposite edges of the pull-apart basin ∼20 km apart. The organization of this seismicity into families of numerous repeating earthquakes suggests an aseismic process linked to fault healing and rapid reloading in a critically stressed zone. By December 2022, two months before the earthquake, activity had migrated to a cluster located along the path that rupture was to follow during the initial stage of the earthquake. These observations show that the pull-apart basin where rupture started was progressively deforming in a succession of bursts before the earthquake. This regional-scale deformation is closely linked with the transitional nature of geodynamics and kinematics influenced by large-scale fault interactions in the surrounding area. The location of the epicenter near the northern termination of the rupture of the 1822 M7.4 earthquake suggests that the ∼45 km long Narlı sub-rupture which constituted the first stage of this giant earthquake was closing a long-present seismic gap between the DSF and the EAF.

Imaging the Volve ocean-bottom field data with the Upside-down Rayleigh-Marchenko method

Geophysical Journal International - Thu, 03/27/2025 - 00:00

SummaryOcean-bottom seismic acquisitions are gaining widespread popularity across a variety of subsurface applications. However, the high cost of these systems often necessitates receiver geometries with large intervals between ocean-bottom cables or nodes. The upside-down Rayleigh-Marchenko (UD-RM) method has been recently proposed as an effective solution for accurate redatuming and imaging of sparse seabed data. In this paper, we present the first successful application of the UD-RM method to field data. We demonstrate that in the presence of a shallow seabed, an improved data pre-processing workflow is necessary to generate more accurate input wavefields compared to the one produced by the workflow presented in the original paper. To validate the proposed processing workflow, the UD-RM method is initially tested on a synthetic dataset that mimics the Volve field data (referred to as the Volve synthetic dataset); this is followed by its application to a 2D line of the Volve ocean-bottom cable dataset. Subsequently, the field dataset is subsampled by retaining only 25 percent of the total receivers to numerically validate the UD-RM method’s capability to handle sparse receiver arrays. The resulting images reveal that the UD-RM method, when paired with our enhanced data processing workflow, can effectively handle surface-related multiples, internal multiples, and sparse receiver arrays, producing accurate imaging results without the need for costly and labor-intensive multiple removal processes. Finally, we provide theoretical insights and numerical evidence supporting the necessity of source-side deghosting prior to redatuming. While a pre-processing workflow that omits source-side deghosting can offer some practical advantages, we show that this ultimately produces blurrier images compared to those obtained using source-side deghosted input data.

Designing Full Waveform Inverse Problems: a Combined Data and Model Approach

Geophysical Journal International - Thu, 03/27/2025 - 00:00

SummaryFull waveform inversion (FWI) has the potential to provide high-resolution insights into subsurface structures. However, its adoption, particularly in 3D multiparameter applications, has been limited by high computational costs. This study addresses this challenge by introducing an optimized experimental design (OED) method that simultaneously optimizes source placement and model parameterization. The result is an optimized survey design and a compressed model representation that maximizes the information content. By reducing the source layout by approximately 50% and compressing the model by approximately 90%, this approach significantly reduces computational demands, allowing the use of fast convergence inversion algorithms such as the Gauss-Newton method. The OED calculation is reduced from a typical $\mathcal {O}(n^3)$ complexity, as in eigenvalue-based criteria, to $\mathcal {O}(n \log _2n)$ with the newly introduced wavelet transform-based criterion. Additionally, a post-acquisition source-receiver pair optimization method is developed, demonstrating that while random selection captures high information content, the proposed OED criterion effectively minimizes the number of required simulations. This approach further reduces computational cost and facilitates the efficient extraction of compact, high-value datasets from excessively large surveys.

Seismic Imaging of the Ecuadorian Forearc and Arc from Joint Ambient Noise, Local, and Teleseismic Tomography: Catching the Nazca Slab in the Act of Flattening

Geophysical Journal International - Thu, 03/27/2025 - 00:00

SummaryThe Ecuadorian Andes are a complex region characterized by accreted oceanic terranes driven by the ongoing subduction of the oceanic Nazca plate beneath South America. Present-day tectonics in Ecuador are linked to the down-going plate geometry featuring the subduction of the aseismic, oceanic Carnegie Ridge, which is currently entering the trench. Using seismic tomography, we jointly invert arrival times of P and S waves from local and teleseismic earthquakes with surface wave dispersion curves to image the structure of the forearc and magmatic arc of the Ecuadorian Andes. Our dataset includes >100,000 travel-times recorded at 294 stations across Ecuador. Our images show the basement of the central forearc is composed of accreted oceanic terranes with high elastic wavespeeds. Inboard of the Carnegie Ridge, the westernmost forearc and coastal cordilleras display relatively low Vp and Vs and high Vp/Vs values, which we attribute to the increased hydration and fracturing of the overriding plate due to the subduction of the thick oceanic crust of the Carnegie Ridge. We additionally image across-arc differences in magmatic architecture. The frontal volcanic arc overlies accreted terranes and is characterized by low velocities and high Vp/Vs indicative of partial melt reservoirs which are limited to the upper crust. In contrast, the main arc displays regions of partial melt across a wider range of depths. The Subandean zone of Ecuador has two active volcanoes built on continental crust suggesting the arc is expanding eastward. The mid to lower crust does not show indications of being modified from the magmatic process. We infer that the slab is in the process of flattening as a consequence of early-stage subduction of the buoyant Carnegie Ridge.

Developing a clearer understanding of permafrost thaw risk in Alaska

Phys.org: Earth science - Wed, 03/26/2025 - 21:11

In the Arctic, permafrost plays a crucial role in building infrastructure. However, as the region warms and permafrost thaws, infrastructure is threatened as the ground shifts beneath the built environment. Unfortunately, the full extent of the risks associated with this process is not yet realized, but researchers are working to address this knowledge gap.

Forecasting the future of Southern Ocean ecosystems

Phys.org: Earth science - Wed, 03/26/2025 - 19:27

Ecosystems in the Southern Ocean, the body of water surrounding Antarctica, are under threat from climate change. The area's inhabitants, from whales to krill to phytoplankton, face changes such as a loss in sea ice and rising ocean temperatures. If species that are unique to the area, such as the Antarctic toothfish, dwindle in population as a result, this decrease could affect fishery operations and lead to cascading socioeconomic and geopolitical consequences.