Mike Müller-Petke

• Professor
• Head of Department at Leibniz Institute for Applied Geophysics

The pore-size distribution (PSD) of geologic materials is an important rock parameter to understand the flow of water in the subsurface. PSDs can be obtained from sieving analyses, mercury porosimetry measurements, and imaging techniques, but none of these methods is available for in situ measurements. Nuclear magnetic resonance (NMR) measurements...

MRSmatlab is a manufacturer-independent software tool for processing, modeling, and inversion of surface nuclear magnetic resonance data. Intended as an open platform, MRSmatlab has been growing over the past few years by connecting researchers and making the latest research available to the community. We have developed insights into yet unpublishe...

In the recent years, slim-borehole nuclear magnetic resonance (NMR) tools, designed for shallow hydrogeological applications, have become available. We have developed and improved the performance of one of them to detect and characterize hydrocarbon contamination. Our objectives were (1) to generally increase the vertical resolution of NMR logs bel...

The application of surface nuclear magnetic resonance (NMR) measurements, although proven to be valuable for various hydrogeological issues, is in practice often limited to single 1D surveys because measurement progress is slow. First, large stacking rates are necessary to overcome the low signal-to-noise ratio and, second, time and effort are requ...

This study investigates the longitudinal (T1) to transverse (T2) relaxation time ratios in unconsolidated geological materials to determine how they vary across different geological units. Assessing the T1/T2 ratio can inform about the validity of the presumed relationship between T1 and T2 relaxation times in steady-state surface NMR modeling (i.e...

Extensive pumping, storm floods or sea-level rise can lead to regional and local-scale processes of saltwater intrusion into coastal aquifers. Particularly when exacerbated by the impacts of climate change, these processes can threaten freshwater resources and thus drinking water supplies and need to be prevented by investigation and monitoring, fo...

Surface nuclear magnetic resonance (SNMR) is a geophysical technique that is directly sensitive to liquid water. In this study, we evaluate the feasibility of SNMR for detecting and characterizing an englacial channel within Rhonegletscher, Switzerland. Building on prior information on Rhonegletscher’s englacial hydrology, we conducted a proof-of-c...

Extending surface nuclear magnetic resonance (SNMR) with prepolarization (PP) enables mobile compact SNMR layouts, that are promising for soil moisture investigations. The prepolarization introduces additional parameters into the SNMR experiment, and therefore predicting the resolution performance of a specific PP SNMR layout becomes more complicat...

Coastal aquifers, the transition zone between freshwater and saltwater, show large salinity contrasts in the subsurface. Salinity is a key parameter to understand coastal groundwater flow dynamics and consequently also geochemical and microbial processes. For mapping porewater salinity, a variety of methods exists, mainly using electrical conductiv...

Submarine groundwater discharge (SGD) at the interface of land and sea is likely an important part of the global hydrological cycle and has started to attract the attention of a growing interdisciplinary scientific community. While before the year 2000 only a few papers about that topic are listed in the ISI Web of Science, by now about 100 publica...

The Bloch–Siegert effect is relevant for NMR experiments where components of the excitation pulse other than the circularly polarized component have an influence on the evolution of the magnetization of the spin system under consideration. For linearly polarized excitation fields this happens at amplitudes higher than roughly one tenth of the magni...

Subterranean estuaries are connective zones between inland aquifers and the open sea where terrestrial freshwater and circulating seawater mix and undergo major biogeochemical changes. They are biogeochemical reactors that modify groundwater chemistry prior to discharge into the sea. We propose that subterranean estuaries of high-energy beaches are...

Subterranean estuaries are connective zones between inland aquifers and the open sea where terrestrial freshwater and circulating seawater mix and undergo major biogeochemical changes. They are biogeochemical reactors that modify groundwater chemistry prior to discharge into the sea. We propose that subterranean estuaries of high-energy beaches are...

A recent study demonstrated that in small-scale prepolarized surface nuclear magnetic resonance (SNMR-PP) measurements with a footprint of a few square meters, customized PP switch-off ramps can serve as an efficient excitation mechanism, eliminating the requirement for a conventional oscillating excitation pulse. This approach enables the detectio...

Oberflächen-NMR (SNMR) ist ein etabliertes Verfahren der angewandten Geophysik zur zerstörungsfreien hydrogeologischen Charakterisierung des Untergrundes bis in ca. 150m Tiefe. In jüngerer Zeit haben auch kleinräumige Oberflächen-NMR-Messungen mit einer Grundfläche von wenigen Quadratmetern an Interesse in der Bodengeophysik gewonnen. Aufgrund der...

Understanding the interaction of terrestrial freshwater and seawater in the subterranean estuary (STE) is an important factor when considering nutrient fluxes from land to sea. State-of-the-art research describes the STE by a tide-induced upper saline recirculation cell, a freshwater discharge tube and a deep saltwater wedge. However, recent numeri...

Because of its mobility and ability to investigate exposed surfaces, single-sided (SiS) nuclear magnetic resonance (NMR) technology enables new application felds in geosciences. To test and assess its corresponding potential, we compare longitudinal (T1) and transverse (T2) data measured by SiS NMR with those of conventional geoscientific laborator...

Surface-NMR (SNMR) is a well-established geophysical method for the hydrogeological characterization of aquifers down to a depth of about 150m. Most recently, small-scale SNMR with a footprint of a few m² has gained interest within the soil physics community [1,2]. Due to the interrelation between loop size and excited subsurface volume, it is nece...

Surface nuclear magnetic resonance (sNMR) is an electromagnetic hydrogeophysical method directly sensitive to liquid phase water in the upper ≈\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-6...

Oberflächen-NMR (SNMR) ist ein etabliertes Verfahren der angewandten Geophysik zur zerstörungsfreien hydrogeologischen Charakterisierung des Untergrundes bis in ca. 150m Tiefe. In jüngerer Zeit haben auch kleinräumige SNMR-Messungen mit einer Grundfläche von wenigen Quadratmetern an Interesse in der Bodengeophysik gewonnen. Aufgrund der Beziehung z...

Plain Language Summary Surface nuclear magnetic resonance (SNMR) is a geophysical method that can directly detect water in the subsurface. Typically, an electromagnetic pulse at a frequency determined by the local Earth's magnetic field is applied to stimulate the water molecules. After this excitation, the water molecules relax to their equilibriu...

Moisture stored in near surface soils is a key feature for a manifold of ecological processes. The soil, being the interface between the atmosphere and the lithosphere, plays a crucial role for the transport of water and the dissolved substances therein. At present, there are no suitable direct methods to determine soil moisture content at the requ...

In the past few years, small‐scale (2 m) prepolarized surface nuclear magnetic resonance (SNMR) has gained increasing interest in the research community. As recent studies demonstrated, the application of a strong prepolarization field enhances the SNMR signal of coils with a footprint <1 m² up to a level that even enables investigations in urban a...

Subterranean estuaries the, subsurface mixing zones of terrestrial groundwater and seawater, substantially influence solute fluxes to the oceans. Solutes brought by groundwater from land and solutes brought from the sea can undergo biogeochemical reactions. These are often mediated by microbes and controlled by reactions with coastal sediments, and...

In nonlinear inversion of geophysical data, improper initial approximation of the model parameters usually leads to local convergence of the normal Newton iteration methods, despite enforcing constraints on the physical properties. To mitigate this problem, we present a globally convergent Homotopy continuation algorithm to solve the nonlinear leas...

As one main objective in hydrogeophysics, we aim at describing hydraulic properties in the subsurface in at least two dimensions. However, due to the limited resolution and ambiguity of the individual methods, those images often remain blurry. We present a methodology to combine two measuring methods, magnetic resonance tomography (MRT) and electri...

Geophysical methods can characterize aquifer systems non-invasively and are particularly helpful to image the complex depositional structure of the subsurface.Among these, ground-penetrating radar (GPR) is an effective tool for detailed investigations of shallow subsurface geometry, but provides only limited information on hydraulic properties.Magn...

Surface nuclear magnetic resonance (SNMR) is a well-established technique for the hydrogeological characterization of the subsurface up to depths of about 150m. Recently, SNMR has been adapted to investigate also the shallow unsaturated zone with small surface loop setups. Due to the decreased volume, a pre-polarization (PP) field prior to the clas...

Magnetic Resonance Sounding (MRS) can image the spatial distribution of hydrologically relevant parameters in in the subsurface. However, the application of MRS is often limited by its low signal-to-noise ratio. The use of adiabatic excitation pulses show promising features to overcome this limitation. In this work, we study practical consideration...

Surface nuclear magnetic resonance (SNMR) is a well-established technique for the hydrogeological characterization of the subsurface up to depths of about 150m. Recently, SNMR has been adapted to investigate also the shallow unsaturated zone with small surface loop setups. Due to the decreased volume, a pre-polarization (PP) field prior to the clas...

Surface-NMR measurements commonly suffer from low signal-to-noise ratios. In recent years, with the introduction of multi-channel surface-NMR instruments, the technique of remote-reference noise cancellation (RNC) was developed and significantly improved the applicability of surface-NMR. The current formulation of RNC requires a reference loop to b...

Due to multi-exponential decay-time properties of the subsurface volume units or layers, magnetic resonance sounding (MRS) relaxation data exhibit a multi-exponential behavior. MRS inverse problem in a multi-exponential modeling framework brings about a very large size of the parameter space which is computationally costly. In this paper, a fast an...

Oberflächen-NMR ist ein etabliertes Verfahren der angewandten Hydrogeophysik zur hydrogeologischen Charakterisierung des Untergrundes bis in maximal 150m Tiefe. Mit Hilfe von Präpolarisations-Spulen, welche das messbare NMR-Signal in Abhängigkeit von der verwendeten Stromstärke um mehr als eine Größenordnung erhöhen können, ist der Einsatz von Ober...

Nuclear-Magnetic Resonance (NMR) is a powerful tool for groundwater system imaging. Ongoing developments in surface NMR, e.g., multi channel devices, allow for investigations of increasingly complex subsurface structures. However, with growing complexity of the field cases, the availability of appropriate software to accomplish the in-depth data an...

Since several years, surface nuclear magnetic resonance (SNMR) is a well-established method for the hydrogeological characterization of the subsurface up to depths of 150m. When used with small surface loops of only a few square meters, SNMR suffers from low signal-to-noise ratios. This limits the methods applicability in urban areas or areas with...

Measurements of surface nuclear magnetic resonance (NMR) combined with a prepolarisation previous to the conventional spin excitation are expected to enable non-invasive soil moisture investigations even in urban areas with high environmental noise. To test this expectation, we conducted prepolarised surface NMR using a very small coil (figure-of-e...

Plain Language Summary Surface nuclear magnetic resonance (surface NMR) is a geophysical technique that can directly measure the presence of water in the subsurface. An NMR sounding typically uses a large loop to generate a pulse that excites water into a higher energy level. As the water relaxes back to the equilibrium state, it releases energy th...

Magnetic resonance sounding (MRS) signals are always corrupted by random noise. Although time-frequency peak filtering (TFPF) has been proven to be an effective method to suppress the random noise, it shows shortcomings when processing the oscillating high-frequency MRS signal at about 2 kHz. In this study, a new method combining empirical mode dec...

This document provides the basics to understand and handle the Matlab based software MRSmatlab (Müller-Petke et al. 2016), that allows the processing, modelling and inversion of surface nuclear magnetic resonance (SNMR) data sets.

Oberflächen-NMR ist eine seit mehreren Jahren etablierte Methode zur hydrologischen Charakterisierung des Untergrundes bis in max. 150m Tiefe. Mit den vorhandenen 1D und 2D Messkonfigurationen ist es möglich aus den Oberflächen-NMR Messungen, die räumliche Verteilung von Wassergehalt (Porosität) und hydraulischer Leitfähigkeit abzuleiten. Aufgrund...

Surface nuclear magnetic resonance (SNMR) data typically suffer from very low signal-tonoise ratio. Two of the main sources of noise that generate low signal-to-noise ratios are powerlines and railways that create harmonic noise. Some noise cancellation strategies for mitigating this harmonic noise have been presented. However, when the frequency o...

Surface nuclear magnetic resonance is a valuable technique that provides insight into the distribution of water content and relaxation time, thus revealing hydraulic properties in the subsurface. Recent research has introduced a new measurement layout that allows for time-efficient imaging of the 2D parameter distribution. Furthermore, for 1D inves...

Hydrological parameters like porosity, salinity, and hydraulic conductivity are key for understanding the subsurface. Hydrogeophysical investigations can lead to ambiguous results, particularly in the presence of clay and saltwater. A combination of magnetic resonance sounding (MRS) and vertical electrical sounding (VES) is known to provide insight...

Adiabatic half-passage (AHP) pulses show great promise for significantly enhancing the signal-to-noise ratio of the surface nuclear magnetic resonance (NMR) free-induction decay measurement. Performing an AHP requires that the frequency sweep terminates when the transmit frequency is equal to the Larmor frequency, a condition that demands accurate...

Beim Betrieb von Brunnen in Fe-haltigem Grundwasser gehören die chemische und biologische Brunnenverockerung zu den häufigsten Alterungsprozessen, die einen starken negativen Einfluss auf die Effizienz von Grundwasserförderbrunnen haben. Um die Effizienz auch langfristig zu erhalten, werden in der Literatur neben chemischen und mechanischen Regener...

The capability of nuclear magnetic resonance (NMR) relaxometry to characterise hydraulic properties of iron-oxide-coated sand and gravel was evaluated in a laboratory study. Past studies have shown that the presence of paramagnetic iron oxides and large pores in coarse sand and gravel disturbs the otherwise linear relationship between relaxation ti...

The technique of surface nuclear magnetic resonance (SNMR) has been widely used for hydrological investigations in recent years. Unfortunately, the detected SNMR signals are limited to tens of nanovolts and are thus susceptible to environmental noise. While prepolarization pulses to enhance the detected signal amplitudes are common in laboratory ap...

The nuclear magnetic resonance (NMR) technique has become popular in groundwater studies because it responds directly to the presence and mobility of water in a porous medium. There is a need to conduct laboratory experiments to aid in the development of NMR hydraulic conductivity models, as is typically done in the petroleum industry. However, the...

Different mobile measurement technologies for nuclear magnetic resonance (NMR) are introduced and compared in this study and their potential application in tunnels and mines within clay formations is evaluated. In doing so, laboratory NMR meas-urements using Opalinus clay samples with varying water contents are presented and used to simulate and re...

Magnetic resonance tomography using elongated transmitter and in-loop receiver arrays (MRTetra) is designed to efficiently image the groundwater in two-dimensional. However, due to resolution limitations and the volume effect, the structure and boundary features of the aquifer are ambiguous. We make use of the GPR reflection data to generate struct...

Other than commonly assumed the relaxation times observed in the electrical low-frequency range (1 mHz – 40 kHz) of natural porous media like sandstones and tuff stones cannot be directly related to the dominant (modal) pore throat sizes, measured (e.g.) with mercury intrusion porosimetry (MIP). Working with a great variety of sandstones from very...

Nuclear magnetic resonance (NMR) is a well established laboratory / borehole method to characterize the storage and transport properties of rocks due to its direct sensitivity to the corresponding pore fluid saturation (water or oil) and pore sizes. For petrophysical applications there are several different NMR laboratory devices commercially avail...

Die elektrischen Eigenschaften im Niederfrequenzbereich der Spektral Induzierten Polarisation (SIP) von silikatisch gebundenen, porösen Medien werden maßgeblich durch der Porenstruktur, der Art des Sättigungsfluids, der geochemischen Zusammensetzung und den Oberflächeneigenschaften (wie z.Bsp. der Oberflächenladung oder der Kationenaustauschkapazit...

Surface nuclear magnetic resonance (surface NMR) has up to now rarely been applied to 3D subsurface modeling. Inversion approaches currently in use are smooth inversion techniques that are not useful for identifying sharp geologic boundaries. Although they are already computationally expensive, the resulting models are restricted to imaging the sub...

To produce reliable estimates of aquifer properties using surface nuclear magnetic resonance (NMR), an accurate forward model is required. The standard surface NMR forward model assumes that excitation occurs through a process called on-resonance excitation, which occurs when the transmit frequency is set to the Larmor frequency. However, this cond...

Nuclear magnetic resonance (NMR) measurements provide direct sensitivity to hydrogen-bearing fluids and their interactions with the pore space. As such NMR is used in near-surface geophysics to determine water content and to estimate hydrogeologic properties such as pore size and hydraulic conductivity. This special section covers the recent advanc...

For the surface nuclear magnetic resonance sounding method, we investigate the tradeoff between stacking and the number of different pulse moments by analyzing the a posteriori model covariance matrix. It is shown that a better determination of the model parameters is obtained by increasing the number of pulse moments compared with increasing the s...

The method of nuclear magnetic resonance (NMR) has found widespread application because NMR captures information from one of the key elements of life, the hydrogen proton. The use of NMR in the field of geophysics ranges from laboratory studies to borehole logging and surface-based techniques applied in the context of, for instance, hydrogeophysics...

The technique of surface NMR has been applied to image 1D, 2D and recently 3D subsurface structures. Although limited resolution is reported for imaging deep 3D structures using a coincident loop configuration, high resolution is obtained for shallow 2D structures by including separated loop configurations. We adapt the concept of separated transmi...

Surface nuclear magnetic resonance (surface-NMR) is a promising technique for exploring shallow subsurface aquifer structures. Surface-NMR can be applied in environments that are characterized as a 1-D layered Earth. The technique utilizes a single loop and is referred to as magnetic resonance sounding. The technique referred to as magnetic resonan...

The noninvasive detection and characterization of subsurface aquifer structures demands geophysical techniques. Surface nuclear magnetic resonance (SNMR) is the only technique that is directly sensitive to hydrogen protons and, therefore, allows for unambiguous detection of subsurface water. Traditionally, SNMR utilizes large surface coils for both...

The technique of surface nuclear magnetic resonance (surface-NMR) provides information on porosity and hydraulic conductivity that are highly valuable in a hydrogeological context. However, the applicability of surface-NMR is often limited due to bad signal-to-noise ratio. In this paper we provide detailed insight into the technique of harmonic no...

Development in instrumentation and data analysis of surface nuclear magnetic resonance has recently moved on from 1d soundings to 2d surveys, opening the method to a larger field of hydrological applications. Current analysis of 2d data sets, however, does not incorporate relaxation times and is therefore restricted to the water content distributio...

In this paper three different despiking methods for surface-NMR data are investigated and compared. Two of these are applied in the time domain: A threshold is determined that identifies and marks a spiky event. Afterward, the marked time sequence is substituted with zeros or with the mean value of the signal amplitude of the measurement repetition...

Magnetic resonance sounding (MRS) has increasingly become an important method in hydrogeophysics because it allows for estimations of essential hydraulic properties such as porosity and hydraulic conductivity. A resistivity model is required for magnetic resonance sounding modelling and inversion. Therefore, joint interpretation or inversion is fav...

A crucial component in sustainable freshwater management is the reliable and cost-effective characterization of groundwater aquifers. A technique that allows noninvasive characterization of shallow (<100 m) aquifers is surface nuclear magnetic resonance (surface NMR). The measured parameter longitudinal relaxation time T1 provides a link to pore-sc...

Surface-Nuclear-Magnetic-Resonance (surface-NMR) has shown a continuous development towards a frequently used and established hydro-geophysical tool during the last decades. However, the measured signals are as low as few tens of nanovolts and therefore often contaminated by significant amounts of electromagnetic noise. Consequently, surface-NMR ha...

In this study we are analyzing the balance between number of data points and data quality in SNMR survey design. In SNMR the number of data points increase with the number of pulse moments and data quality increase with the number of records at each pulse moment (stack size). The premise for our analysis is that the total amount of records is fixed...

The prediction of hydraulic conductivity K from nuclear magnetic resonance (NMR) measurements has been performed primarily in sandstones. In hydrogeological applications, however, unconsolidated material is more prevalent. Compared to sandstones, unconsolidated sediments can show pore sizes up to several millimeters. The known (semi-)empiric relati...

We present a new loop configuration provides high subsurface resolution for Magnetic Resonance Tomography (MRT) by only one measurement. Model resolution matrix and radius are analyzed based on singular value de composition (SVD) of the MRT kernels including regularization. We take two shapes of the transmitter loop, square and rectangle, and two c...

A talik is a layer or body of unfrozen ground that occurs in permafrost due to an anomaly in thermal, hydrological, or hydrochemical conditions. Information about talik geometry is important for understanding regional surface water and ground water interactions as well as sub-lacustrine methane production in thermokarst lakes. Due to the direct mea...

Nuclear Magnetic Resonance (NMR) can provide key information such as porosity and permeability for hydrological characterization of geological material. In particular the NMR transverse relaxation time T2 is used to estimate permeability since it reflects a pore-size dependent relaxation process. The measurement sequence (CPMG) usually consists of...

By using multi-channel MRS equipment the opportunity to cancel harmonic noise from MRS data can be taken (Walsh, 2008). In addition to the MRS measurement loop, one or more reference loops are placed in an appropriate distance (remote reference) to measure the noise simultaneously. In the postprocessing of the data, the electromagnetic (EM) transfe...

In order to do hydraulic modelling for simulating the salt-/fresh water dynamics, the parameters porosity, salinity and hydraulic conductivity are needed. We present a methodology retrieve them by the joint analysis of magnetic resonance (MRS) and and vertical electric (VES) soundings. Both data sets are jointly inverted for resistivity, water cont...

For assessing the impact of climate changes on salinity of coastal aquifers, numerical modelling needs to be done. As input, the spatial distribution of the parameters porosity, hydraulic conductivity and salt concentrations is needed. Airborne resistivity data are available that gives hints to fluid conductivity. Magnetic resonance soundings (MRS)...

For reliably predicting the impact of climate changes on salt/freshwater systems below barrier islands, a long-term hydraulic modelling is inevitable. As input we need the parameters porosity, salinity and hydraulic conductivity at the catchment scale, preferably non-invasively acquired with geophysical methods. We present a methodology to retrieve...