William Benjamin Frank

• Ph.D.
• Professor (Assistant) at Massachusetts Institute of Technology

Referred to as slow slip events, the transient aseismic slip that occurs along plate boundaries can be indirectly characterized through colocated seismicity, such as tectonic tremor and low-frequency earthquakes (LFEs). Using the timing of cataloged LFE and tremor activity in Guerrero, Mexico, and northern Cascadia, I decompose the interaseismic GP...

Capable of reaching similar magnitudes to large megathrust earthquakes [Mw (moment magnitude) > 7], slow slip events play a major role in accommodating tectonic motion on plate boundaries through predominantly aseismic rupture. We demonstrate here that large slow slip events are a cluster of short-duration slow transients. Using a dense catalog of...

We develop a single‐station tremor spectrum template detection method that we applied to continuous seismic data recorded by the Mexican National Seismological Service broadband stations. This allows for an unprecedented long‐term analysis of tectonic tremor in Mexico over multiple slow slip events (SSEs). We only detect tremor that are within prev...

Slow slip transients on faults can last from seconds to months and stitch together the earthquake cycle. However, no single geophysical instrument is able to observe the full range of slow slip because of bandwidth limitations. Here, we connect seismic and geodetic data from the Mexican subduction zone to explore an instrumental blind spot. We esta...

Plain Language Summary The relative motion of tectonic plates on Earth leads to the accumulation of elastic energy at plate boundaries. Tectonic faults can release this energy, either suddenly by rapid (m/s) slip that generates seismic shaking (i.e., during earthquakes) or gently by slow (mm/year to m/year) slip. Subseismic slip can release just as...

We report the first catalog of low‐frequency earthquakes in the Hikurangi subduction zone, located beneath the Kaimanawa Range of the North Island at 50 km depth, downdip of regularly recurring (every 4–5 years) deep M7 slow slip events. To systematically detect low‐frequency earthquakes within the regional continuous seismic data, we utilized a ma...

The coupling at the interface between tectonic plates is a key geophysical parameter to capture the frictional locking across plate boundaries and provides a means to estimate where tectonic strain is accumulating through time. Here, we use both interferometric radar (InSAR) and Global Navigation Satellite System (GNSS) data to investigate the plat...

The coupling at the interface between tectonic plates is a key geophysical parameter to capture the frictional locking across plate boundaries, and provides a means to estimate where tectonic strain is accumulating through time. Here, we use both interferometric radar (InSAR) and GNSS data to investigate the plate coupling of the Hikurangi subducti...

The matched-filter technique is an effective way to detect repeats, or near-repeats, of a seismic source, but prior identification of an event from that source to use as a template is required. We propose a recursive matched-filter approach to systematically explore earthquake swarms, here applied to a swarm of volcanic long-period seismicity benea...

Approximately 2 yr (2010–2011) of continuous seismic records from a subset of the Antarctic component of the Polar Earth Observing Network (POLENET‐ANET) seismic network deployed in West Antarctica are used to compute the nine components of the correlation tensor between each pair of stations in the network. Rayleigh wave velocity information from...

How faulting processes lead to a large earthquake is a fundamental question in seismology. To better constrain this pre‐seismic stage, we create a dense seismic catalog via template matching to analyze the precursory phase of the Mw 6.1 L’Aquila earthquake that occurred in central Italy in 2009. We estimate several physical parameters in time, such...

Earthquake catalogs are essential to analyze the evolution of active fault systems. The background seismicity rate, or rate of earthquakes that are not directly triggered by other earthquakes, directly relates to the stressing rate, a crucial quantity for understanding the seismic hazards. Determining the background seismicity rate is challenging b...

Seismic anisotropy in the flat slab region of Mexico is compared with tectonic tremor activity. The anisotropy is observed in three separate horizontal layers using a novel technique with receiver functions. Those layers are identified as the continental crust and the subducted flat oceanic slab and a thin (∼10 km thick) remnant mantle wedge betwee...

The seismic catalog of earthquakes that have occurred in a given fault zone is a window into the tectonic processes that occur at depth. These earthquakes rupture faults when the fault can no longer support the stress built-up by tectonic motion. When an earthquake occurs spontaneously from tectonic stresses, this mainshock will trigger aftershocks...

The 2016 M7.8 Kaikōura earthquake is one of the most complex earthquakes in recorded history, with significant rupture of at least 21 crustal faults. Using a matched‐filter detection routine, precise cross‐correlation pick corrections, and accurate location and relocation techniques, we construct a catalog of 33,328 earthquakes between 2009 and 202...

Low‐frequency earthquakes (LFEs) are detected within tremor, as small, repetitive, impulsive low‐frequency (1–8 Hz) signals. While the mechanism causing this depletion of the high‐frequency content of their signal is still debated, this feature may indicate that the source processes at the origin of LFEs are different from those for regular earthqu...

This catalog is a subset of Frank et al., 2014 [ref 2] catalog, for which Farge et al., 2020 [ref 1] estimated seismic moments and corner frequencies. The archive contains a catalog of events detection times, location, seismic moments and corner frequency, and a bulletin listing the time of detection on each station used for characterization. Plea...

The 2014 Iquique seismic crisis in Chile, culminating with a Mw 8.1 earthquake on 1 April, highlights a complex unlocking of the Northern Chilean subduction that has been considered a seismic gap since 1877. During the year preceding this event, at least three clusters of seismic activity have been reported: in July 2013 and January and March 2014....

Slow-Slip Events (SSEs) haven been observed along the Hikurangi subduction zone of the North Island of New-Zealand. They occur both in the shallow plate interface (<15km depth) and at the deeper end of the seismogenic-zone (>30km depth). Some slow slip events in New-Zealand are also accompanied by tectonic tremors, although tremor is not as common...

We present a new automated earthquake detection and location method based on beamforming (or back projection) and template matching and apply it to study the seismicity of the Southwestern Alps. We use beamforming with prior knowledge of the 3‐D variations of seismic velocities as a first detection run to search for earthquakes that are used as tem...

Key Points: • Automated earthquake detection combining beamforming, event classification and template matching applied to the Southwestern Alps. • Systematic analysis of earthquake clustering by estimating the fractal dimension of time series of earthquake occurrence. • Burst-like seismicity in fractured medium in the Briançonnais and Dora Maira vs...

We report new observations of triggered tectonic tremor in three regions in South America along the plate boundary between the Nazca and South America plates: southern Chile, Ecuador, and central Colombia. In these regions, tremor was observed during the passage of large‐amplitude surface waves of recent large earthquakes, which occurred in South A...

We present an analytical model based on the idea that afterslip drives seismicity: aftershocks occur when a given level of afterslip is reached in their vicinity. Afterslip is assumed to be governed by a resisting stress that increases as the logarithm of the sliding velocity. This model extends the aftershock migration model of Perfettini et al. (...

After lying dormant for 36 yr, the Tolbachik volcano of the Klyuchevskoy group started to erupt on 27 November 2012. We investigate the preparatory phase of this eruption via a statistical analysis of the temporal behavior of long-period (LP) earthquakes that occurred beneath this volcanic system. The LP seismicity occurs close to the surface benea...

Aftershocks region have been extensively reported to expand logarithmically with time. The associated migration velocity is typically of the order of several km/decade, but can be much larger, especially when observing early aftershock sequences, seismic swarms or tremors. We present here a model for the expansion of aftershock zones based on the i...

We adapt matched-filter searching to a region of sparse stations and seismicity, and demonstrate that earthquake detection can be significantly enhanced. The Earthscope Transportable Array (TA) increased the density of broadband seismometers in New England from 2013 until 2015, allowing for a higher resolution characterization of the regional seism...

Matched‐filter searches are an important tool in modern seismology to detect seismic events. They operate via an algorithm that computes the correlation coefficient between a template event and a sliding window of continuous seismic records. A detection is recorded when the correlation coefficient crosses an established threshold. We present an opt...

Capable of reaching similar magnitudes to large megathrust earthquakes ($M_w>7$), slow slip events play a major role in accommodating tectonic motion on plate boundaries. These slip transients are the slow release of built-up tectonic stress that are geodetically imaged as a predominantly aseismic rupture, which is smooth in both time and space. We...

Matched-filter searches are an important tool in modern seismology to detect seismic events. The algorithm functions by computing the correlation coefficient between a template earthquake and a sliding window of continuous seismic records. A detection is recorded when the correlation coefficient crosses an established threshold. We present an optim...

Low Frequency Earthquakes (LFEs) often occur in conjunction with transient strain episodes, or Slow Slip Events (SSEs), in subduction zones. Their focal mechanism and location consistent with shear failure on the plate interface argue for a model where LFEs are discrete dynamic ruptures in an otherwise slowly slipping interface. SSEs are mostly obs...

Since the discovery of slow slip events, many methods have been successfully applied to model obvious transient events in geodetic time series, such as the widely used network strain filter. Independent seismological observations of tremors or low frequency earthquakes and repeating earthquakes provide evidence of low amplitude slow deformation but...

The postseismic deformation following a large (Mw >7) earthquake is expressed both seismically and aseismically. Recent studies have appealed to a model that suggests that the aseismic slip on the plate interface following the mainshock can be the driving factor in aftershock sequences, reproducing both the geodetic (afterslip) and seismic (aftersh...

Recent studies have reported seismic phenomena that are modulated by small stress perturbations (< 10 kPa), revealing their critically stressed nature. Such observations have been principally been limited to plate interfaces with their occurrence linked to high fluid pore-pressure. In this study, we report observations of nine repeating seismic sou...

Observed along the roots of seismogenic faults where the locked interface transitions to a stably sliding one, low-frequency earthquakes (LFEs) primarily occur as event bursts during slow slip. Using an event catalog from Guerrero, Mexico, we employ a statistical analysis to consider the sequence of LFEs at a single asperity as apoint process, and...

Tectonic tremor (TT) and low-frequency earthquakes (LFEs) have been found in the deeper crust of various tectonic environments globally in the last decade. The spatial-temporal be- haviour of LFEs provides insight into deep fault zone processes. In this study, we examine recurrence times from a 12-yr catalogue of 88 LFE families with ∼730 000 LFEs...

Slow transient slip that releases stress along the deep roots of plate interfaces is most often observed on regional GPS networks installed at the surface. The detection of slow slip is not trivial if the dislocation along the fault at depth does not generate a geodetic signal greater than the observational noise level. Instead of the typical workf...

Studies of low-frequency earthquakes (LFEs) have focused on detecting events within previously-identified tectonic tremor. However, the principal LFE detection tool of matched-filter searches are intrinsically incapable of detecting events that have not already been characterized previously as a template event. In this study, we therefore focus on...

Low-frequency earthquakes (LFEs), which frequently originate from multiplet-generating sources that are closely linked with tectonic tremor in subduction zones around the world, are difficult to observe and characterize due to their low signal-to-noise ratios. This obstacle can be sidestepped by detecting and then stacking all of the multiplets of...

We use data from the Meso-America Subduction Experiment to detect and locate low-frequency earthquakes (LFEs) in the Mexican subduction zone. We use visually-identified templates to perform a network waveform correlation search that produced ~17,000 robustly detected LFEs that form 15 distinct families. Stacking an LFE family's corresponding detect...

The Guerrero seismic gap located in the Central Mexico subduction zone is a hot area of intensive study as it apparently has accumulated, for the last 100 years, sufficient elastic strain to be released in Mw~7.8-8.0 earthquake. Since its installation, the permanent GPS network in Mexico detected 4 large Slow Slip Events (SSE) with a periodicity of...

In this study we analyze the tremors triggered in Guerrero region (Mexico) by the 2010 magnitude 8.8 Chilean Earthquake using mini-seismic array data from the French-Mexican G-GAP project and broadband data from the Servicio Sismologico Nacional of Mexico. The strong dynamic shaking by the earthquake produced the first observed triggered non-volcan...