Normal-faulting Event Research Articles

Insight into the 1 December 2016 Mw 6.2 Juliaca Earthquake, Southern Peru, by InSAR Observations and Field Investigation

On 1 December 2016, an Mw 6.2 earthquake characterized by normal faulting occurred in the highlands of the central Andes in southern Peru, marking the region’s largest shallow event. The occurrence of the earthquake provides a significant chance to gain insight into the regional tectonic deformation and the seismogenic mechanism of the shallow normal-faulting earthquake, as well as the regional potential seismic risk. Here, we first utilize Sentinel-1A interferometric synthetic aperture radar (InSAR) data to extract the coseismic and postseismic deformation associated with this earthquake and then determine the detailed coseismic slip and postseismic afterslip distribution of this event. Coseismic modeling results indicate that the coseismic rupture is mainly characterized by normal faulting with some dextral strike-slip components. Most coseismic slip is confined to a depth range of 2–12 km, indicating an obvious slip deficit area in the shallow fault part. Further postseismic modeling reveals that the majority of afterslip is concentrated at depths of 0 to 5.4 km. The relatively shallow postseismic afterslip makes up for the coseismic slip deficit area to some extent. Through a joint analysis of the inversions, seismic data, and regional geology and geomorphology, we infer that the occurrence of this 2016 normal-faulting event is a result of regional gravitational collapse. In addition, we investigate the relationship between the 2016 earthquake and great historical earthquakes near the subduction zone of the central Andes and find that the 2016 event is likely promoted in advance by these events through our calculations of the coseismic and postseismic Coulomb stress changes. Finally, we should pay more attention to the nearby Falla Huaytacucho-Condoroma fault and the western segment of the Vilcanota Fault because of their relatively high stress loading.

The July 2020 Mw 6.3 Nima Earthquake, Central Tibet: A Shallow Normal-Faulting Event Rupturing in a Stepover Zone

Abstract On 22 July 2020, an Mw 6.3 earthquake with a predominantly normal-faulting mechanism struck the Yibug Caka fault zone, central Tibet, where the overall tectonic environment is characterized by left-lateral strike-slip motion. This event offers a chance to gain insight into the tectonic deformation and the cause of shallow normal-faulting earthquakes in this little studied region. Here, we use Sentinel-1A/B Interferometric Synthetic Aperture Radar data to investigate the coseismic and postseismic deformation related to this earthquake. The earthquake ruptured a previously mapped West Yibug Caka fault and is dominated by normal slip with a peak value of 1.9 m at depth of 6.9 km. Postseismic deformation analysis indicates that the observed subsidence signals of up to ∼4.7 cm are a consequence of afterslip. Most of the afterslip is confined at depths between 0.8 and 8.4 km, peaking at 0.27 m at depth of 6.1 km. The significant coseismic slip and afterslip involved in the earthquake highlights a complex interaction between the major normal fault and the secondary synthetic fault. By an integrated analysis of the inversions, regional geology geomorphology, fault kinematics, and seismicity background, we propose a tectonic model that attributes the occurrence of this normal-faulting event to the release of extensional stress in a stepover zone controlled by the northeast-striking sinistral strike-slip Riganpei Co fault and Bu Zang Ai fault. Compared with that the structural stepover often acts as a barrier to affect the propagation of earthquake rupture, our study demonstrates that the failure of a stepover may potentially induce the occurrence of earthquake along the bounding strike-slip faults.

Late Devonian transition from advancing to retreating subduction in the SW Central Asian Orogenic Belt: Insights from multiple deformation and magmatic events in the southern Yili Block, NW China

In order to better constrain the Late Paleozoic tectonic evolution of the SW Central Asian Orogenic Belt, we conducted field structural investigations, zircon U-Pb dating, whole-rock geochemical and Sr-Nd isotopic studies on the meta-sedimentary rocks and intruding granites and mafic dykes in the Dahalajunshan area, southern Yili Block of NW China. Our results allow us to recognize five tectonic/magmatic events. Field-scale and microscopic structures of the low-grade meta-sedimentary rocks showed a regional top-to-the-SE thrusting (Event 1). Undeformed granites that contain dioritic enclaves (Event 2) crosscut the regional foliations and thus post-date Event 1 after ca. 379–369 Ma. Mafic dykes intruded all these rocks after ∼328 Ma (Event 4–1), posterior to brittle-ductile thrusting (N-S contraction) (Event 3) and prior to normal faulting (N-S extension) (Event 4–2). All the magmatic rocks formed in a subduction-related setting. The granites and dioritic enclaves derived from a mixing of crustal- and mantle-derived sources variously modified by slab-derived hydrous melts. The primary magma of the diabase dykes derived from a mantle source modified by the slab fluids with 5% crustal contamination. Variation from regional compression (ductile and brittle-ductile thrusting) to extension (normal faulting) and increasing mantle input in arc-related magmatism reveals a transition from Early Paleozoic advancing subduction (events 1 to 3) to Late Paleozoic retreating subduction (events 4–1 and 4–2) of the Junggar oceanic plate beneath the Yili Block.

Sentinel-1 observation of 2019 Mw 5.7 Acipayam earthquake: A blind normal-faulting event in the Acipayam basin, southwestern Turkey

Rapid disaster response will provide significant information to relevant responding agencies. On 20 March 2019, an Mw 5.7 earthquake struck the Acipayam basin in southwestern Turkey, which is the largest event to occur in the basin. Here, we use Sentinel-1A interferometric synthetic aperture radar (InSAR) data to investigate the cosesimic deformation related to the Acipayam earthquake. The ascending and descending interforegrams suggest the normal faulting during this earthquake, with the maximum line of sight (LOS) displacements of 4.6 cm and 4.8 cm, respectively. The fault geometric parameters and a detailed coseismic distributed slip model of this event are retrieved by using geodetic data for the first time. Though the coseismic interferograms don’t show enough polarity changes to ascertain the dip orientation of the rupture fault, we regard the northeast-dipping fault as the causative fault by a joint analysis of the residuals plots, 2.5 dimensional (2.5D) deformation field, field investigation results, regional geomorphic feature and overall distribution of aftershock (4.0 < Mw < 4.9). The inversion results show that coseismic rupture was mainly dominated by normal faulting with minor sinistral strike-slip components. The rupture fault is a blind normal fault and the main slip is concentrated in the depth range of 3∼9.5 km with a maximum slip of approximately 0.33 m at a depth of ∼6 km. The InSAR-determined geodetic seismic moment is 3.96 × 1017 Nm corresponding to Mw 5.7. Our model resolution test supports these interpretations for the Acipayam earthquake. Based on the coseismic Coulomb stress change, we find that this 2019 event increases the stress loading in the northwestern and southeastern segment of the rupture fault plane and possibly triggers the subsequent Mw 4.8 and Mw 4.9 earthquakes. The mechanism of the determined seismogenic fault may be helpful to evaluate seismic hazards and understand the evolution of the Acipayam basin.

The 1996 Mw 6.6 Lijiang earthquake: Application of JERS-1 SAR interferometry on a typical normal-faulting event in the northwestern Yunnan rift zone, SW China

The northwestern Yunnan rift zone in the Yunnan Province of China is a seismically active region located along the western boundary of the Sichuan–Yunnan Block on the eastern margin of the Qinghai–Tibetan Plateau. An earthquake with a magnitude of 6.6 (Mw) occurred in this region on February 3, 1996. The Lijiang earthquake was the largest normal-faulting event to occur along the western boundary of the Sichuan–Yunnan Block in the last 40years. In this study, we used L-band JERS-1 (Japanese Earth Resources Satellite-1) SAR data sets from two descending orbits to detect surface deformation signals surrounding the epicentral region in order to estimate the source parameters through an inversion of the displacement fields. The results indicated that the earthquake can be explained by slip along two segments of the ∼N–S trending listric normal fault, named the Lijiang–Daju fault. Coseismic deformation patterns and slip distributions revealed that the earthquake consisted of two sub-events, which were also suggested by seismological results. Based on an analysis of the static Coulomb stress change, the second sub-event was likely triggered by the first sub-event. The central segment of the Lijiang–Daju fault, which has an eastward-convex geometry, did not rupture during the earthquake. This phenomenon was probably related to a geometrical discontinuity at the fault-bend area of the Lijiang–Daju fault.

Source Parameters of the 2003–2004 Bange Earthquake Sequence, Central Tibet, China, Estimated from InSAR Data

A sequence of Ms ≥ 5.0 earthquakes occurred in 2003 and 2004 in Bange County, Tibet, China, all with similar depths and focal mechanisms. However, the source parameters, kinematics and relationships between these earthquakes are poorly known because of their moderately-sized magnitude and the sparse distribution of seismic stations in the region. We utilize interferometric synthetic aperture radar (InSAR) data from the European Space Agency’s Envisat satellite to determine the location, fault geometry and slip distribution of three large events of the sequence that occurred on 7 July 2003 (Ms 6.0), 27 March 2004 (Ms 6.2), and 3 July 2004 (Ms 5.1). The modeling results indicate that the 7 July 2003 event was a normal-faulting event with a right-lateral slip component, the 27 March 2004 earthquake was associated with a normal fault striking northeast–southwest and dipping northwest with a moderately oblique right-lateral slip, and the 3 July 2004 event was caused by a normal fault. A calculation of the static stress changes on the fault planes demonstrates that the third earthquake may have been triggered by the previous ones.

Source study of three moderate size recent earthquakes in the Guerrero seismic gap

We study three recent earthquakes of different types in the Guerrero seismic gap zone with M ≥ 6.5: the 15 July 1996 Guerrero near-coast interplate earthquake (Mw = 6.6), the 18 April 2002 Guerrero near-trench interplate earthquake (Mw = 6.7), and the 11 December 2011 Guerrero normal-faulting inslab earthquake (Mw = 6.5). We compute the slip distributions, estimate source parameters, and model strong ground motions with the finite-fault stochastic method. We use different methods to estimate source parameters in order to observe differences in stress drop and radiated seismic energy among these events. The similarity in seismic magnitude gives us the opportunity to compare our results for the three different types of earthquake and interpret them in terms of the tectonic environments and seismic hazard. We analyze the peak ground accelerations and their relation with the stress drop. We simulated ground motions with the stochastic method. The model parameters are validated against recordings and a stress drop of 3, 15, and 70 MPa is estimated for the near-trench interplate, near-coast interplate, and normal-faulting inslab events, respectively. The near-trench interplate event has the lowest radiated seismic energy and the lowest rupture velocity. This is reflected in the energy to moment ratio of 2.17 × 10−6, 4.52 × 10−6, and 3.96 × 10−6 for the near-trench interplate, near-coast interplate, and normal-faulting inslab events, respectively. We define asperities using two different criteria: (1) based on average displacement and (2) maximum displacement. The asperity area for the near-coast and near-trench interplate events represents about 23 and 24–25 % of the total rupture area, which in the case of the normal-faulting inslab event, it is only 19 and 23 % based on average and maximum displacement, respectively.

Aftershocks of the December 7, 2012 intraplate doublet near the Japan Trench axis

On December 7, 2012, a pair of large Mw 7.2 intraplate earthquakes occurred near the Japan Trench axis off Miyagi, northeast Japan. This doublet consisted of a deep reverse-faulting event followed by a shallow normal-faulting event. Aftershock observations using conventional and newly developed ultra-deep ocean bottom seismographs in the trench axis area showed that the shallow normal-faulting event occurred in the subducting Pacific plate just landward of the trench axis. The shallow normal-faulting aftershock activity indicated that in-plate tension in the incoming/subducting Pacific plate extends to a depth of at least 30 km, which is deeper than before the 2011 Tohoku-Oki earthquake, whereas in-plate compression occurs at depths of more than 50 km. Hence, we concluded that the neutral plane of the in-plate stress is located between depths of 30 and 50 km near the trench axis.

The December 7, 2012 Japan Trench intraplate doublet (Mw 7.2, 7.1) and interactions between near-trench intraplate thrust and normal faulting

A pair of large earthquakes ruptured within the Pacific plate below the Japan Trench about 14s apart on December 7, 2012. The doublet began with an Mw 7.2 thrust event 50–70km deep, followed by an Mw 7.1–7.2 normal-faulting event in the range 10–30km deep about 27km to the south–southwest. The deep lithosphere thrust earthquake is the largest such event to be recorded seaward of the rupture zone of the great March 11, 2011 Tohoku Mw 9.0 earthquake. It follows an extensive intraplate normal-faulting aftershock sequence since 2011 extending up to 100km east of the trench. Many small normal faulting aftershocks of the doublet occurred along a 60km-long trench-parallel-trend beneath the inner trench slope. The complex overlapping signals produced by the doublet present challenges for routine long-period moment tensor inversion procedures, but the inadequacy of any single point-source inversion was readily evident from comparisons of different data sets and solutions using different frequency bands. We use a two double-couple inversion of W-phase signals to quantify the doublet characteristics, along with an iterative deconvolution of P-wave signals that extracts a compatible three sub-event sequence. The occurrence of a large deep compressional event near the trench several years subsequent to a great megathrust event is similar to a sequence that occurred in the central Kuril Islands between 2006 and 2009, and appears to be associated with stress changes caused by the preceding interplate thrusting and intraplate normal faulting. Recent large deep compressional events in the Philippine Trench and northern Kermadec Trench regions may be influenced by strain accumulation on adjacent locked interplate megathrusts. Regions having more pronounced curvature of the subducting plate may have unrelaxed bending stresses, facilitating occurrence of large deep thrust faulting in advance of future megathrust failures, as was observed in 1963 in the central Kuril Islands region but not in the gently curving Pacific plate offshore of the great Tohoku event.

Near-simultaneous great earthquakes at Tongan megathrust and outer rise in September 2009

The Earth's largest earthquakes and tsunamis are usually caused by thrust-faulting earthquakes on the shallow part of the subduction interface between two tectonic plates, where stored elastic energy due to convergence between the plates is rapidly released. The tsunami that devastated the Samoan and northern Tongan islands on 29 September 2009 was preceded by a globally recorded magnitude-8 normal-faulting earthquake in the outer-rise region, where the Pacific plate bends before entering the subduction zone. Preliminary interpretation suggested that this earthquake was the source of the tsunami. Here we show that the outer-rise earthquake was accompanied by a nearly simultaneous rupture of the shallow subduction interface, equivalent to a magnitude-8 earthquake, that also contributed significantly to the tsunami. The subduction interface event was probably a slow earthquake with a rise time of several minutes that triggered the outer-rise event several minutes later. However, we cannot rule out the possibility that the normal fault ruptured first and dynamically triggered the subduction interface event. Our evidence comes from displacements of Global Positioning System stations and modelling of tsunami waves recorded by ocean-bottom pressure sensors, with support from seismic data and tsunami field observations. Evidence of the subduction earthquake in global seismic data is largely hidden because of the earthquake's slow rise time or because its ground motion is disguised by that of the normal-faulting event. Earthquake doublets where subduction interface events trigger large outer-rise earthquakes have been recorded previously, but this is the first well-documented example where the two events occur so closely in time and the triggering event might be a slow earthquake. As well as providing information on strain release mechanisms at subduction zones, earthquakes such as this provide a possible mechanism for the occasional large tsunamis generated at the Tonga subduction zone, where slip between the plates is predominantly aseismic.

The 2005 Heidelberg and Speyer earthquakes and their relationship to active tectonics in the central Upper Rhine Graben

We determine the source parameters of three minor earthquakes in the Upper Rhine Graben (URG), a Cenozoic rift, using waveforms from permanent and temporary seismological stations. Two shallow thrust-faulting events (M L = 2.4 and 1.5) occurred on the rift shoulder just south of Heidelberg in March 2005. They indicate a possible movement along the sediment–crystalline interface due to tectonic loading from the near-by Odenwald. In February 2005, an earthquake with a normal-faulting mechanism occurred north of Speyer. This event (M L = 2.8) had an unusual depth of about 22 km and a similar deep normal-faulting event occurred there in 1972 (M L = 3.2). Other lower crustal events without fault plane solutions are known from 1981 and 1983. At such a depth, inside the lower crust, ductile behaviour instead of brittle faulting is commonly assumed and used for geodynamic modelling. Based on the newly available fault plane solutions we can confirm the brittle, extensional regime in the upper and lower crust in the central to northern URG indicated in earlier studies.

The Oaxaca Earthquake of 30 September 1999 (Mw = 7.5): A Normal-faulting Event in the Subducted Cocos Plate

Research Article| January 01, 2000 The Oaxaca Earthquake of 30 September 1999 (Mw = 7.5): A Normal-faulting Event in the Subducted Cocos Plate S. K. Singh; S. K. Singh 1Instituto de Geofísica, UNAM, México 2Instituto de Ingeniería, UNAM, México Search for other works by this author on: GSW Google Scholar M. Ordaz; M. Ordaz 2Instituto de Ingeniería, UNAM, México Search for other works by this author on: GSW Google Scholar L. Alcántara; L. Alcántara 2Instituto de Ingeniería, UNAM, México Search for other works by this author on: GSW Google Scholar N. Shapiro; N. Shapiro 1Instituto de Geofísica, UNAM, México Search for other works by this author on: GSW Google Scholar V. Kostoglodov; V. Kostoglodov 1Instituto de Geofísica, UNAM, México Search for other works by this author on: GSW Google Scholar J. F. Pacheco; J. F. Pacheco 1Instituto de Geofísica, UNAM, México Search for other works by this author on: GSW Google Scholar S. Alcocer; S. Alcocer 2Instituto de Ingeniería, UNAM, México 3Centro Nacional de Prevención de Desastres, México Search for other works by this author on: GSW Google Scholar C. Gutiérrez; C. Gutiérrez 3Centro Nacional de Prevención de Desastres, México Search for other works by this author on: GSW Google Scholar R. Quaas; R. Quaas 2Instituto de Ingeniería, UNAM, México 3Centro Nacional de Prevención de Desastres, México Search for other works by this author on: GSW Google Scholar T. Mikumo; T. Mikumo 1Instituto de Geofísica, UNAM, México Search for other works by this author on: GSW Google Scholar E. Ovando E. Ovando 2Instituto de Ingeniería, UNAM, México Search for other works by this author on: GSW Google Scholar Seismological Research Letters (2000) 71 (1): 67–78. https://doi.org/10.1785/gssrl.71.1.67 Article history first online: 09 Mar 2017 Cite View This Citation Add to Citation Manager Share Icon Share Twitter LinkedIn Tools Icon Tools Get Permissions Search Site Citation S. K. Singh, M. Ordaz, L. Alcántara, N. Shapiro, V. Kostoglodov, J. F. Pacheco, S. Alcocer, C. Gutiérrez, R. Quaas, T. Mikumo, E. Ovando; The Oaxaca Earthquake of 30 September 1999 (Mw = 7.5): A Normal-faulting Event in the Subducted Cocos Plate. Seismological Research Letters 2000;; 71 (1): 67–78. doi: https://doi.org/10.1785/gssrl.71.1.67 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentBy SocietySeismological Research Letters Search Advanced Search The two large earthquakes to occur in México in 1999 were both normal-faulting, intraplate events in the subducted Cocos Plate. There is, however, a significant difference in their locations with respect to the coast, and, hence, with respect to the strongly coupled plate interface. The 15 June 1999 Tehuacán earthquake (H ∼60 km; Mw = 7.0) was located about 200 km inland from the coast (Singh et al., 1999) and in this sense was a typical intraplate event in the subducted slab. The Oaxaca earthquake of 30 September 1999 (H ∼45 km; Mw =... You do not have access to this content, please speak to your institutional administrator if you feel you should have access.

A Preliminary Report on the Tehuacan, Mexico Earthquake of June 15, 1999 (Mw = 7.0)

INTRODUCTION Large intermediate-depth, normal-faulting earthquakes in the subducted Cocos plate result in significant damage to the cities and the villages of the Mexican altiplano. Some examples are the earthquake of January 15, 1931 ( M 7.8), which caused heavy damage to the city of Oaxaca (Barrera, 1931; Singh et al., 1985); and the earthquakes of August 28, 1973 ( Mw 7.0) and October 24, 1980 ( Mw 7.0), which resulted in deaths and damages in the states of Veracruz, Puebla, and Oaxaca (Singh and Wyss, 1976; Yamamoto et al., 1984). It has been suggested that the great earthquake of June 19, 1858, which caused severe damage to inland towns in the state of Michoacain, including its capital city of Morelia, and to Mexico City may also have been an intermediate-depth, normal-faulting event (Singh et al., 1996). Such earthquakes (M## 6.5), which have occurred in the states of Oaxaca, Veracruz, and Puebla, are shown...

Static stress changes in extensional regimes: An application to southern Apennines (Italy)

AbstractThe analysis of static stress changes due to co-seismic dislocations has been widely applied in recent years to study the variation in failure stress on well-known segmented seismogenic faults. These studies assert that earthquakes induce changes in static stress on neighboring faults that may delay, advance, or trigger impending earthquakes. So far, most of the investigations have focused on California strike-slip faults and, more recently, on thrust faults. In this work, we study the static stress changes in an extensional tectonic setting. Following Okada (1992), we calculate static stress changes caused by normal-faulting earthquakes in the southern Apennines (Italy) using a 3D dislocation model in an elastic half-space. We first studied the static stress changes produced by the 1980 Irpinia earthquake. This normal-faulting event consisted of four fault segments that ruptured together within 40 sec. The last two subevents occurred 20 and 40 sec after the nucleation on two normal faults parallel to the main one. Because the rupture of these subvents are separated by a sufficiently long time interval, we assume that, before each subevent, the dynamic stress has reached its static configuration. Therefore, we analyze the static stress changes caused by each subevent in order to determine the variations of the initial conditions for subsequent ruptures. Moreover, we applied our procedure to study the static stress changes after the 1980 Irpinia earthquake on the fault zone where the 1990 and 1991 Potenza earthquakes (M ≈ 5) occurred. Our calculations indicate that, even if the amount of stress change depends on the fault geometry assumed for the 20-sec subevent of the Irpinia fault, the static stress increased on the Potenza fault after the 1980 Irpinia earthquake. This event also increased the static stress on seismogenic faults that are believed to have ruptured in the 1732 and 1857 earthquakes (M ≈ 6.5). In these calculations, we have considered the effect of a regional extensional stress field whose minimum principal axis is horizontal and oriented 216° N. The results show that the 1980 Irpinia earthquake increased the static stress by roughly 1 bar on the 1732 fault zone. Right lateral strike-slip faults oriented nearly E-W, such as the Potenza fault, are favorably oriented with respect to the total stress resulting from the extensional regional stress field and the coseismic stress induced by the Irpinia earthquake. Finally, we investigate the static stress changes caused by several historical earthquakes that occurred along the southern Apennines seismogenic belt. Most of the large historical earthquakes occurred in areas of static stress increase, yielding evidence for fault interaction.

The great Mexican earthquake of 19 June 1858: Expected ground motions and damage in Mexico City from a similar future event

Abstract The description of the great earthquake of 19 June 1858 is unusual: damage and high intensities were reported both in the state of Michoacan and in Mexico City. Although a coastal epicenter for this earthquake cannot be ruled out, the reports agree better with an intermediate-depth (about 50 km), normal-faulting event in the subducted Cocos plate. A careful examination of the reports of this event and other normal-faulting events below the Mexican altiplano suggests that a likely location is 18.0 °N, 100.8 °W, near the epicenter of the 6 June 1964 (M7.3, H = 55 km) event. This location is 220 km SW of the city. The magnitude of the earthquake is estimated to be about 7.7. We synthesize expected ground motions in CU, a hill-zone site in the city, from an event similar to that of 1858, using records from the 23 May 1994 earthquake (18.0 °N, 100.6 °W, H = 50 km, M5.7) as an empirical Green's function and stress parameter, Δσ, of 50, 160, and 300 bar. The expected peak horizontal acceleration in CU of Δσ = 160 bar is about 30 gals. Similar acceleration was recorded in CU during the 1985, Michoacan earthquake (M8.0). We compute expected ground motions at many sites in Mexico City using empirical transfer functions and random vibration theory and compare these motions and the expected damage in the city with those from the 1985 Michoacan earthquake. Results show that the overall expected damage during the postulated earthquake is ⅔ and 1⅓ of that during the Michoacan earthquake for Δσ = 160 and 300 bar, respectively. A greater percentage of low-rise construction, which constitute about 80% of the total in the city, will be damaged during the postulated earthquake than during the Michoacan earthquake. The expected ground motions for Δσ = 50 bar are smaller at all periods than those from the Michoacan earthquake. As the present building code for Mexico City contemplates coastal earthquakes of magnitude greater than 8.0, the case of Δσ = 50 bar is not of interest in this article. This preliminary study suggests a need for a more careful evaluation of expected ground motion in the Valley of Mexico from the postulated earthquake and its impact on the current design spectra of the city.