Volcanic geomorphology—an overview

As a result of the serious consequences of the 2010 Eyjafjallajokull eruption (Iceland) on civil aviation, 52 volcanologists, meteorologists, atmospheric dispersion modellers and space and ground-based monitoring specialists from 12 different countries (including representatives from 6 Volcanic Ash Advisory Centres and related institutions) gathered to discuss the needs of the ash dispersal modelling community, investigate new data-acquisition strategies (i.e. quantitative measurements and observations) and discuss how to improve communication between the research community and institutions with an operational mandate. Based on a dedicated benchmark exercise and on 3 days of in-depth discussion, recommendations have been made for future model improvements, new strategies of ash cloud forecasting, multidisciplinary data acquisition and more efficient communication between different communities. Issues addressed in the workshop include ash dispersal modelling, uncertainty, ensemble forecasting, combining dispersal models and observations, sensitivity analysis, model variability, data acquisition, pre-eruption forecasting, first simulation and data assimilation, research priorities and new communication strategies to improve information flow and operational routines. As a main conclusion, model developers, meteorologists, volcanologists and stakeholders need to work closely together to develop new and improved strategies for ash dispersal forecasting and, in particular, to: (1) improve the definition of the source term, (2) design models and forecasting strategies that can better characterize uncertainties, (3) explore and identify the best ensemble strategies that can be adapted to ash dispersal forecasting, (4) identify optimized strategies for the combination of models and observations and (5) implement new critical operational strategies.

/pdf/future-developments-in-modelling-and-monitoring-of-volcanic-8bbfhu6h1j.pdf

Future developments in modelling and monitoring of volcanic ash clouds: outcomes from the first IAVCEI-WMO workshop on Ash Dispersal Forecast and Civil Aviation

Lahars and debris flows: characteristics and impacts

By infusing blood vessels with gas-filled microbubbles and using rapid ultrasound imaging to detect the bubbles, super-resolution imaging of an entire vessel system has been achieved in a rat brain. See Letter p.499
 Conventional clinical ultrasound imaging offers a resolution of, at best, sub-millimetre scale due to fundamental limits of diffraction. Claudia Errico et al. demonstrate a new technique based on ultrasound imaging at ultrafast frame that has sufficiently high resolution at large depths to enable whole-organ mapping of microvasculature. The underlying technique is similar to that of optical localization super-resolution microscopy and is based on fast tracking of transient signals from a sub-wavelength contrast agent — here inert gas microbubbles that are intravenously injected into the blood system. The authors demonstrate the technique by reconstructing the brain microvasculature of a living rat.

pdf/imaging-techniques-super-resolution-ultrasound-57rs391mnm.pdf

Imaging techniques: Super-resolution ultrasound

Natural disasters are extreme events within the earth's system that result in death or injury to humans, and damage or loss of valuable goods, such as buildings, communication systems, agricultural land, forest, natural environment etc. The economic losses due to natural disasters have shown an increase with a factor of eight over the past four decades, caused by the increased vulnerability of the global society, but also due to an increase in the number of weather-related disasters. For the management of natural disasters a large amount of multi -temporal spatial data is required. Satellite remote sensing is the ideal tool for disaster management, since it offers information over large areas, and at short time intervals. Although it can be utilised in the various phases of disaster management, such as prevention, preparedness, relief, and reconstruction, in practice up till now it is mostly used for warning and monitoring. During the last decades remote sensing has become an operational tool in the disaster preparedness and warning phases for cyclones, droughts and floods. The use of remote sensing data is not possible without a proper tool to handle the large amounts of data and combine it with data coming from other sources, such as maps or measurement stations. Therefore, together with the growth of the remote sensing applications, Geographic Information Systems have become increasingly important for disaster management. This chapter gives a review of the use of remote sensing and GIS for a number of major disaster types.

/pdf/remote-sensing-for-natural-disaster-management-25yt74x7md.pdf

Remote sensing for natural disaster management

Cartographic modelling of erosion in pyroclastic flow deposits of Mount Pinatubo, Philippines

The measurement of the shear wave velocities (Vs) of soils is an important aspect of geotechnical and earthquake engineering, due to its direct relation to the shear modulus (G), which in turn influences the stress–strain behavior of geomaterials. Vs can be directly measured or estimated using a variety of onsite tests or in a laboratory. Methods such as downhole PS logging require boreholes and may not be logistically and economically feasible in all situations. Many researchers have estimated Vs from other geotechnical parameters, such as standard penetration test resistance (SPT-N), by means of empirical correlations. This paper aimed to contribute to this subject by developing an empirical relationship between Vs and SPT-N. Data from twenty sites in Metro Manila were obtained from geotechnical investigation reports. Vs profiles of the same sites were also acquired using the refraction microtremor method. New empirical relationships were developed for all, sandy, and clayey soil types, using a non-linear regression method that is applicable for Metro Manila soils. Statistical evaluation and comparison of the proposed correlations with other previous works suggested the viability of the empirical model.

https://www.mdpi.com/2076-3417/12/16/8067/pdf?version=1660288611

Empirical Correlation between Standard Penetration Resistance (SPT-N) and Shear Wave Velocity (Vs) for Soils in Metro Manila, Philippines

A coastal portion of the Greater Metro Manila Area, Philippines, is situated primarily on Quaternary Alluvium deposits which are likely to liquefy. Liquefaction is a hazard that occurs when loosely packed, saturated sediments at or near the ground surface lose its strength caused by an earthquake. Currently, the standard in determining a site’s soil properties and liquefaction potential is by using conventional geotechnical techniques such as the Standard Penetration Test (SPT). However, this method has disadvantages in terms of cost, logistics, and as well as workforce. The Screw Driving Sounding (SDS) test was developed to estimate equivalent SPT parameters such as N-value and Fines Content which are then used for liquefaction analysis. This paper presents the comparative analysis between SDS and SPT in selected schools in Greater Metro Manila Area, Philippines. Moreover, soil classification and site-specific liquefaction potential evaluation were also estimated using the data acquired from the SDS test. Overall, the result of the study proves that the SDS test is an effective alternative method for soil investigation and estimation of the liquefaction potential.

The use of screw driving sounding in soil assessment in Metro Manila, Philippines

The 1994 Mw 7.1 Mindoro Earthquake and the 2017 Mw 5.9 Batangas Earthquake Sequence both occurred in offshore southern Batangas and devastated southern Luzon and Mindoro. These earthquakes exhibited NW-striking right-lateral slip in an area presumably defined by a WNW-striking left-lateral fault, therefore implying the existence of previously unmapped offshore faults. High resolution multibeam bathymetry grid and subbottom profiles revealed a conjugate strike-slip fault system under an approximately EW-directed extension. NW-striking right-lateral faults (F1 Faults: Central Mindoro Fault, Aglubang River Fault, and Batangas Bay Fault System) bound the western part of the study area. On the other hand, a series of almost parallel NE-trending left-lateral and normal faults (F2 Faults: Macolod Corridor, North Verde Fault System, Central Verde Fault System, South Verde Fault, and Northeast Mindoro Fault System) approach the F1 faults from the northeast. The distribution of the 1994 and 2017 earthquakes suggests that the possible rupture areas for these events are the Aglubang River Fault and the southwest Batangas Bay Fault System, respectively. These two traces appear to be connected and a restraining bend is suggested to have acted as a rupture barrier between the two events. Coulomb stress transfer modeling showed that the 1994 earthquake promoted the failure of the 2017 earthquake. Furthermore, results from the stress transfer models showed stress increase on the F1 faults (Batangas Bay Fault System and Central Mindoro Fault) and the northern F2 faults (North Verde Fault System and Central Verde Fault System). The newly recognized faults redefine the knowledge of the neotectonic structure of the area but are still consistent with the ongoing east-west extension in southern Luzon and the overall extension in northern Central Philippines. These faults pose seismic hazards, and more studies are needed to determine their seismogenic potential.

/pdf/seafloor-structures-and-static-stress-changes-associated-qyydirbl.pdf

Seafloor Structures and Static Stress Changes Associated With Two Recent Earthquakes in Offshore Southern Batangas, Philippines

Evaluation of passive seismic horizontal-to-vertical spectral ratio (hvsr) for rapid site-specific liquefaction hazard assessment

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