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The Superstition Hills Fault (SHF) exhibits a rich spectrum of slip modes, including M 6+ earthquakes, afterslip, quasi‐steady creep, and both triggered and spontaneous slow slip events (SSEs). Following 13 years of quiescence, creepmeters recorded 25 mm of slip during 16–19 May 2023. Additional sub‐events brought the total slip to 41 mm. The event nucleated on the northern SHF in early‐May and propagated bi‐laterally at rates on the order of kilometers per day. Surface offsets reveal a bi‐modal slip distribution, with slip on the northern section of the fault being less localized and lower amplitude compared to the southern section. Kinematic slip models confirm systematic variations in the slip distribution along‐strike and with depth and suggest that slip is largely confined to the shallow sedimentary layer. Observations and models of the 2023 SSE bear a strong similarity to previous slip episodes in 1999, 2006, and 2010, suggesting a characteristic behavior. Plain Language Summary: Studying the mechanical properties and behavior of faults is essential for understanding earthquake ruptures. In this study, we investigate a recent slip event on the Superstition Hills Fault (SHF), which has a well‐documented record of slip. A notable aspect of the SHF is that it periodically undergoes "slow slip events" (SSEs), where the fault slips and releases energy without any accompanied ground shaking. During May‐July 2023, the SHF experienced a major SSE for the first time in 13 years. Our analysis shows that it was the largest documented SSE on the SHF and released equivalent energy to a magnitude 4.5 earthquake. We also find that the spatial pattern of fault slip is very similar to several previous slip events in 1999, 2006, and 2010, suggesting that the SHF has a tendency to slip in a characteristic manner. Key Points: We document a recent spontaneous slow slip event (SSE) on the Superstition Hills Fault using creepmeter, Interferometric Synthetic Aperture Radar, Global Navigation Satellite System, and field measurementsOver 41 mm of slip occurred from mid‐May to mid‐July 2023, with moment release corresponding to a Mw 4.5 earthquakeThe kinematics of the 2023 event are remarkably similar to several previous SSEs, suggesting a characteristic rupture process [ABSTRACT FROM AUTHOR]

The EU-TecNet monitoring network uses customized three-dimensional extensometers to record transient deformations across individual faults. This paper presents the first results from two newly established monitoring points in the Balkan Mountains in Bulgaria. The data from Saeva Dupka, recorded across an EEN-WWS striking fault, show sinistral strike-slip along the fault and subsidence of the southern block. Much of the subsidence occurred around the time of the distal MW = 5.6 Pernik Earthquake. An important transient deformation event, which began in autumn 2012, was reflected by significant compression and following extension, across the monitored fault. The data from Bacho Kiro, recorded across a NE–SW striking fault, show sinistral strike-slip along the fault and subsidence of the north-western block. The same important deformation event was reflected by changes in the strike-slip, dip-slip, and horizontal opening/closing trends. These results have been compared to data from other monitoring points in the Western Carpathians, External Dinarides, and Tian Shan. Many of the sites show evidence of simultaneous displacement anomalies and this observation is interpreted as a reflection of the plate-wide propagation of a tectonic pressure pulse towards the end of 2012.

This paper presents the results of direct 3−D fault displacement monitoring along the northern shore of Hornsund Fjord, SW Spitsbergen, Svalbard. The fault displacements have been recorded using three permanently installed optical−mechanical crack gauges since 2009. The monitoring data from all three sites provided evidence for a remarkable slip event that lasted from September 2011 to May 2012. The cause is discussed in some detail with consideration given to both exogenic (temperature changes, surface processes) and endogenic processes (isostatic rebound and regional seismicity). It is proposed that transient fault slips recorded had a tectonic origin and were caused by approximately W−E oriented compression corresponding to regional compression in the Svalbard area.

This work presents the results of 3-D movements of faults occurring in the Dědičná štola Gallery in the Rychlebské hory Mts. during the period between 2014 and 2017. The faults were monitored by TM-71 extensometers. The detected fault slip is nonlinear and is affected by short transient periods of acceleration. One dominant and a series of minor transient fault slip accelerations were recognised. The recorded accelerations were induced by switching two compressional stress/strain states - WNW-ESE to NW-SE compression corresponding to the stress field of the Western European stress domain and to NNE-SSW corresponding to the stress field of the NW part of the Carpathian stress domain. The extensional state, oriented NW-SE, corresponding to gravitational spreading due to the Rychlebské hory Mts. uplift, was recognised. [ABSTRACT FROM AUTHOR]

The EU-TecNet fault displacement monitoring network records three-dimensional displacements across specifically selected tectonic structures within the crystalline basement of central Europe. This paper presents a study of recent and active tectonics at Zapadni Cave in northern Bohemia (Czech Republic). It extends previous geological research by measuring speleothem damage in the cave and monitoring displacements across two fault structures situated within the Lusatian Thrust Zone. The speleothem damage reflects strike-slip displacement trends: the WSW-ENE striking fault is associated with dextral strike-slip displacement while the NNW-SSE striking fault is associated with sinistral strike-slip displacement. These measurements demonstrate that the compressive stress σ1 is located in the NW or SE quadrant while the tensile stress σ3 is oriented perpendicular to σ1, i.e. in the NE or SW quadrant. The in situ fault displacement monitoring has confirmed that movements along the WSW-ENE striking fault reflect dextral strike-slip while movements along the NNW-SSE striking fault reflect sinistral strike-slip. In addition, however, monitoring across the NNW-SSE striking fault has demonstrated relative vertical uplift of the eastern block and, therefore, this fault is characterised by oblique movement trends. The fault displacement monitoring has also shown notable periods of increased geodynamic activity, referred to as pressure pulses, in 2008, 2010-2011, and 2012. The fact that the measured speleothem damage and the results of fault displacement monitoring correspond closely confirms the notion that, at this site, the compressive stress σ1 persists in the NW or SE quadrant. The presented results offer an insight into the periodicity of pressure pulses, demonstrate the need for protracted monitoring periods in order to better understanding geodynamic processes, and show that it is possible to characterise the displacements that occur across individual faults in a way that cannot be accomplished from geodetic measurements obtained by Global Navigation Satellite Systems. [ABSTRACT FROM AUTHOR]