intensity attenuation with distance for large subduction ... et … · the pedernales earthquake...

Intensity attenuation with distance for large subduction earthquakes: a

perspective based on earthquake ground effects from the 16 April

2016, Mw 7.8 Pedernales Earthquake (Ecuador).

Franz Livio, K. Chunga, M.F. Ferrario, A.M. Michetti, M. Mulas, F. Ochoa-Cornejo, D. Besenzon.

The

Apr.

16, 2

016

Pede

rnal

es e

arth

quak

e (M

w7.

8)

Earthquake-induced

EnvironmentalEffects (EEEs)Primary – coastaluplift;

Secondary - ground cracks, mass movements, lateral spreading,liquefactionphenomena, hydrologicalanomalies, tsunamis, and earthquake lights

Are EEEs and damages scaling similarly

with distance?

Papanikolaou et al 2009 (Geol. Soc. of London Sp. Publ. 316)

Pyrgos 1993 Ms 5.5 Kythira 2006 (Mw 6.7)

Murindo (Colombia),17 and 18 Oct. 1992 (Ms 6.6; Ms 7.3)Mosquera-Machado et al. 2009

- How traditional intensity scales and EEEs relate each other?- Same conclusions for continental vs subduction large earthquakes?- How to exactly integrate the two datasets?

Workflow1 - Data collection and treatment• EEEs• Traditional intensity data (EMS-98)

2 - Macroseismic field• ESI-07• EMS-98

3 - Collection of a reference dataset and attenuationanalysis• Instrumental earthquakes with good source parameters and

macroseismic fields

4 - Comparison of the reference dataset with EMS-98 and ESI-07

5 - An integrated macroseismic field and validationwith the reference earthquakes

Data collectionand analysis

1 - Data collection

2 - Macroseismic field

3 - referencedataset 4 – Comparison

5 - An integratedmacroseismic

field

Foto esempio da supplementary

Earthquake Intensity macroseismic field

1 - Data collection

2 -Macroseismic

field3 - reference

dataset 4 – Comparison5 - An integrated

macroseismic field

298 point observations(sites) – original data integrated with GEER-ATC, 2016

Grouping into ca. 50 IDPs(localities)

Hand-drawing of isoseismals

ESI-07

IGEPN original data; USGS and Colombian Geological Survey(«Did you feel it» questionnaire)

Grouping into 98 IDPs

Hand drawing of isoseismals

EMS-98 MM (Musson et al. 2010)

EMS-98

Ea

rthqu

ake

Inte

nsity

mac

rose

ism

ic fi

eld

EMS-98 ESI-07

Selecting and analyzing a set of referenceearthquakes

1 - Data collection

2 - Macroseismic field

3 -referencedataset

4 – Comparison5 - An integrated

macroseismic field

1 - Data collection

2 - Macroseismic field

3 -referencedataset

4 – Comparison5 - An integrated

macroseismic field

GIS analysis

- a GIS-based approach- IDPs number, distribution- Isoseismals as input data- Gridding (5x5 km)

- Distance statisticsfollowing Bakun and Wentworth (1997)

Intensity = 𝑎𝑎 − (𝑏𝑏 � 𝐷𝐷𝐷𝐷𝐷𝐷𝐷𝐷𝑎𝑎𝐷𝐷𝐷𝐷𝐷𝐷)

Intensity and epicentral distance

Intensity binning for a reference earthquake

(e.g., 1942 Mw 7.8)

0

100000

200000

300000

400000

500000

600000

700000

800000

900000

3 4 5 6 7 8 9 10

Dis

tanc

e(m

eter

s)

Intensity (MM)

1942 Mw 7.8

1 - Data collection

2 - Macroseismic field

3 - referencedataset

4 –Comparison

5 - An integratedmacroseismic

field

1 - Data collection

2 - Macroseismic field

3 - referencedataset 4 – Comparison

5 - An integrated

macroseismic field

Distance binning

Conclusions

1. The Pedernales earthquake produced a maximum intensity of IX ESI−07 along a 70-km-long coastal area.

2. As expected, we observed higher values for ESI-07 in the near field, whereas far-field intensity is well depicted by EMS-98 data.

3. We argue that this is mainly due to the improvement of building quality through time, resulting in a less vulnerable urban environment.

4. A merged database of EMS-98 + ESI-07 intensity data, depict a macroseismic field closer to a reference dataset, likely overcoming both the limitations of EMS-98 and ESI-07.

…further details and the

original datasets as supplementary material

Chunga et al., (2018) - BSSA