Characterization of slow slip rate faults in humid areas: Cimandiri fault zone, Indonesia

Abstract

In areas where regional tectonic strain is accommodated by broad zones of short and low slip rate faults, geomorphic and paleoseismic characterization of faults is difficult because of poor surface expression and long earthquake recurrence intervals. In humid areas, faults can be buried by thick sediments or soils; their geomorphic expression subdued and sometimes undetectable until the next earthquake. In Java, active faults are diffused, and their characterization is challenging. Among them is the ENE striking Cimandiri fault zone. Cumulative displacement produces prominent ENE oriented ranges with the southeast side moving relatively upward and to the northeast. The fault zone is expressed in the bedrock by numerous NE, west, and NW trending thrust‐ and strike‐slip faults and folds. However, it is unclear which of these structures are active. We performed a morphometric analysis of the fault zone using 30 m resolution Shuttle Radar Topography Mission digital elevation model. We constructed longitudinal profiles of 601 bedrock rivers along the upthrown ranges along the fault zone, calculated the normalized channel steepness index, identified knickpoints and use their distribution to infer relative magnitudes of rock uplift and locate boundaries that may indicate active fault traces. We compare the rock uplift distribution to surface displacement predicted by elastic dislocation model to determine the plausible fault kinematics. The active Cimandiri fault zone consists of six segments with predominant sense of reverse motion. Our analysis reveals considerable geometric complexity, strongly suggesting segmentation of the fault, and thus smaller maximum earthquakes, consistent with the limited historical record of upper plate earthquakes in Java.

Identification of active faults in West Java, Indonesia, based on earthquake hypocenter determination, relocation, and focal mechanism analysis

“…The Lembang fault was identified as a left-lateral strike-slip fault with an overall length of 29 km (Afnimar and Rasmid 2015; Daryono 2016). The Cimandiri active fault zone consists of six segments with a predominant sense of reverse motion (Marliyani et al 2016). Based on CSAMT data it is shown that the Lembang and Cimandiri faults are not connected to each other (Sanny 2017).…”

Surabaya earthquake hazard soil assessment

“…Medium-sized shallow earthquakes (M4-5) occur along this fault zone in recent years. Evidence of the movement of this fault can be observed with the presence of river terraces, which are raised along with the movement of faults in this area (Marliyani et al, 2016).…”

Geomorphic Response to Differential Uplift: River Long Profiles and Knickpoints From Guadalcanal and Makira (Solomon Islands)

“…Slope-break knickpoints (Haviv et al, 2010;Kirby and Whipple, 2012) develop in response to a change in the baselevel of the system, forcing the fluvial system from one steady state to another. For example, changes in boundary conditions can result from an increase in rock uplift as a result of the initiation of new faults, the increase in slip rate on existing faults, or permanent eustatic sea-level fall (Wobus et al, 2003(Wobus et al, , 2006Goldrick and Bishop, 2007;Harkins et al, 2007;Marliyani et al, 2016). The slope-break knickpoint transmits the new baselevel to the catchment as a migrating wave through the river system.…”

“…The identification, quantification and analysis of rivers and knickpoints, and other features linked to landscape rejuvenation, routinely utilizes global DEM datasets to investigate regional trends in fluvial geomorphology. Therefore, this remote approach to landscape analysis is especially useful in areas that were previously lacking data owing to either accessibility issues or the subtlety of landscape expression (e.g., Oguchi et al, 2003;Ganas et al, 2005;Marliyani et al, 2016;Menier et al, 2017).…”