I've looked over the install log and realized there is important data in the beginning. Below is the first part of the log. Hope this helps.
Feb 14 14:29:16 iMac InstallAssistant[477]: @(#)PROGRAM:Install PROJECT:Install-1000
Feb 14 14:29:16 iMac InstallAssistant[477]: @(#)PROGRAM:IA PROJECT:InstallAssistant-532
Feb 14 14:29:16 iMac InstallAssistant[477]: Hardware: iMac9,1 @ 2.00 GHz (x 2), 4096 MB RAM
Feb 14 14:29:16 iMac InstallAssistant[477]: Running OS Build: Mac OS X 10.11.3 (15D21)
Feb 14 14:29:16 iMac InstallAssistant[477]: Env: DYLD_NO_FIX_PREBINDING=1
Feb 14 14:29:16 iMac InstallAssistant[477]: Env: PATH=/usr/bin:/bin:/usr/sbin:/sbin
Feb 14 14:29:16 iMac InstallAssistant[477]: Env: PWD=/
Feb 14 14:29:16 iMac InstallAssistant[477]: Env: XPC_FLAGS=0x0
Feb 14 14:29:16 iMac InstallAssistant[477]: Env: XPC_SERVICE_NAME=0
Feb 14 14:29:16 iMac InstallAssistant[477]: Env: SHLVL=1
Feb 14 14:29:16 iMac InstallAssistant[477]: Env: __OSINSTALL_ENVIRONMENT=1
Feb 14 14:29:16 iMac InstallAssistant[477]: Env: CI_DEFAULT_OPENCL_USAGE=0
Feb 14 14:29:16 iMac InstallAssistant[477]: Env: OS_INSTALL=1
Feb 14 14:29:16 iMac InstallAssistant[477]: Env: _=/System/Library/CoreServices/Language Chooser.app/Contents/MacOS/Language Chooser
Feb 14 14:29:17 iMac Unknown[450]: 2016-02-14 14:29:17.402 Language Chooser[449:6847] TSplicedFont failed creating descriptor for:
Feb 14 14:29:17 iMac Unknown[450]: (
Feb 14 14:29:17 iMac Unknown[450]: {
Feb 14 14:29:17 iMac Unknown[450]: UnicodeRange = "<__NSCFCharacterSet: 0x7fbc49439010>";
Feb 14 14:29:17 iMac Unknown[450]: name = NotoSansBuhid;
Feb 14 14:29:17 iMac Unknown[450]: },
Feb 14 14:29:17 iMac Unknown[450]: {
Feb 14 14:29:17 iMac Unknown[450]: UnicodeRange = "<__NSCFCharacterSet: 0x7fbc4aa5cd00>";
Feb 14 14:29:17 iMac Unknown[450]: name = NotoSansHanunoo;
Feb 14 14:29:17 iMac Unknown[450]: },
Feb 14 14:29:18 iMac Unknown[450]: 2016-02-14 14:29:18.040 Language Chooser[449:6847] TSplicedFont failed creating descriptor for:
Feb 14 14:29:18 iMac Unknown[450]: (
Feb 14 14:29:18 iMac Unknown[450]: {
Feb 14 14:29:18 iMac Unknown[450]: UnicodeRange = "<__NSCFCharacterSet: 0x7fbc4acd43c0>";
Feb 14 14:29:18 iMac Unknown[450]: name = NotoSansBuhid;
Feb 14 14:29:18 iMac Unknown[450]: },
Feb 14 14:29:18 iMac Unknown[450]: {
Feb 14 14:29:18 iMac Unknown[450]: UnicodeRange = "<__NSCFCharacterSet: 0x7fbc4acd4470>";
Feb 14 14:29:18 iMac Unknown[450]: name = NotoSansHanunoo;
Feb 14 14:29:18 iMac Unknown[450]: },
Feb 14 14:29:19 iMac Unknown[450]: 2016-02-14 14:29:19.019 Language Chooser[449:6847] TSplicedFont failed creating descriptor for:
Feb 14 14:29:19 iMac Unknown[450]: (
Feb 14 14:29:19 iMac Unknown[450]: {
Feb 14 14:29:19 iMac Unknown[450]: UnicodeRange = "<__NSCFCharacterSet: 0x7fbc4aa843a0>";
Feb 14 14:29:19 iMac Unknown[450]: name = NotoSansBuhid;
Feb 14 14:29:19 iMac Unknown[450]: },
Feb 14 14:29:19 iMac Unknown[450]: {
Feb 14 14:29:19 iMac Unknown[450]: UnicodeRange = "<__NSCFCharacterSet: 0x7fbc4aa84410>";
Feb 14 14:29:19 iMac Unknown[450]: name = NotoSansHanunoo;
Feb 14 14:29:19 iMac Unknown[450]: },
Feb 14 14:29:20 iMac Unknown[450]: 2016-02-14 14:29:20.317 Language Chooser[449:6847] TSplicedFont failed creating descriptor for:
Feb 14 14:29:20 iMac Unknown[450]: (
Feb 14 14:29:20 iMac Unknown[450]: {
Feb 14 14:29:20 iMac Unknown[450]: UnicodeRange = "<__NSCFCharacterSet: 0x7fbc4aa84d40>";
Feb 14 14:29:20 iMac Unknown[450]: name = NotoSansBuhid;
Feb 14 14:29:20 iMac Unknown[450]: },
Feb 14 14:29:20 iMac Unknown[450]: {
Feb 14 14:29:20 iMac Unknown[450]: UnicodeRange = "<__NSCFCharacterSet: 0x7fbc4aa84df0>";
Feb 14 14:29:20 iMac Unknown[450]: name = NotoSansHanunoo;
Feb 14 14:29:20 iMac Unknown[450]: },
Feb 14 14:29:20 iMac InstallAssistant[477]: LSExceptions [0x7fa150c3f5b0] unloaded
Feb 14 14:29:20 iMac InstallAssistant[477]: Can not connect to /var/run/systemkeychaincheck.socket: No such file or directory
Feb 14 14:29:20 iMac InstallAssistant[477]: Using distribution archive from /Volumes/Image Volume/Install OS X El Capitan.app/Contents/SharedSupport/OSInstall.mpkg
Feb 14 14:29:21 iMac Unknown[450]: 2016-02-14 14:29:21.054 Language Chooser[449:6847] TSplicedFont failed creating descriptor for:
Feb 14 14:29:21 iMac Unknown[450]: (
Feb 14 14:29:21 iMac Unknown[450]: {
Feb 14 14:29:21 iMac Unknown[450]: UnicodeRange = "<__NSCFCharacterSet: 0x7fbc4ac98900>";
Feb 14 14:29:21 iMac Unknown[450]: name = NotoSansBuhid;
Feb 14 14:29:21 iMac Unknown[450]: },
Feb 14 14:29:21 iMac Unknown[450]: {
Feb 14 14:29:21 iMac Unknown[450]: UnicodeRange = "<__NSCFCharacterSet: 0x7fbc4acbf9a0>";
Feb 14 14:29:21 iMac Unknown[450]: name = NotoSansHanunoo;
Feb 14 14:29:21 iMac Unknown[450]: },
Feb 14 14:29:22 iMac Unknown[450]: 2016-02-14 14:29:22.023 Language Chooser[449:6847] TSplicedFont failed creating descriptor for:
Feb 14 14:29:22 iMac Unknown[450]: (
Feb 14 14:29:22 iMac Unknown[450]: {
Feb 14 14:29:22 iMac Unknown[450]: UnicodeRange = "<__NSCFCharacterSet: 0x7fbc4acd4860>";
Feb 14 14:29:22 iMac Unknown[450]: name = NotoSansBuhid;
Feb 14 14:29:22 iMac Unknown[450]: },
Feb 14 14:29:22 iMac Unknown[450]: {
Feb 14 14:29:22 iMac Unknown[450]: UnicodeRange = "<__NSCFCharacterSet: 0x7fbc4acd4910>";
Feb 14 14:29:22 iMac Unknown[450]: name = NotoSansHanunoo;
Feb 14 14:29:22 iMac Unknown[450]: },
Feb 14 14:29:22 iMac InstallAssistant[477]: Package Authoring Warning: The installer script defines but doesn't use (and can't install) package id com.apple.pkg.OSUpgrade version 10.11.3.1.
Feb 14 14:29:22 iMac InstallAssistant[477]: Configuring products from SharedSupport folder
Feb 14 14:29:22 iMac InstallAssistant[477]: Install is double-dmg. Not adding chunklist to download list.
Feb 14 14:29:22 iMac InstallAssistant[477]: Using product <OSInstallDVDProduct> based on media at /Volumes/Image Volume/Install OS X El Capitan.app/Contents/SharedSupport at distance 5
Feb 14 14:29:22 iMac InstallAssistant[477]: Using product <OSInstallESDProduct> based on distribution at /Volumes/Image Volume/Install OS X El Capitan.app/Contents/SharedSupport/OSInstall.mpkg at distance 5
Feb 14 14:29:22 iMac InstallAssistant[477]: Checking Software Update catalog URL https://swscan.apple.com/content/catalogs/others/index-10.11-10.10-10.9-mountain lion-lion-snowleopard-leopard.merged-1.sucatalog
Feb 14 14:29:22 iMac InstallAssistant[477]: No available package ref for compatibility update. Ignoring.
Feb 14 14:29:22 iMac InstallAssistant[477]: DM ..F-[DMManager(PrivateMethods) clientConforms:error:]: currentThread=7179=0x1c0b expectedThread=775=0x307
Feb 14 14:29:22 iMac InstallAssistant[477]: No available package ref for compatibility update. Ignoring.
Feb 14 14:29:22 iMac InstallAssistant[477]: DM ..F-[DMManager(PrivateMethods) clientConforms:error:]: currentThread=7179=0x1c0b expectedThread=775=0x307
Feb 14 14:29:22 iMac InstallAssistant[477]: No available package ref for compatibility update. Ignoring.
Feb 14 14:29:22 iMac InstallAssistant[477]: DM ..F-[DMManager(PrivateMethods) clientConforms:error:]: currentThread=7179=0x1c0b expectedThread=775=0x307
Feb 14 14:29:23 iMac Unknown[450]: 2016-02-14 14:29:23.056 Language Chooser[449:6847] TSplicedFont failed creating descriptor for:
Feb 14 14:29:23 iMac Unknown[450]: (
Feb 14 14:29:23 iMac Unknown[450]: {
Feb 14 14:29:23 iMac Unknown[450]: UnicodeRange = "<__NSCFCharacterSet: 0x7fbc4acd09d0>";
Feb 14 14:29:23 iMac Unknown[450]: name = NotoSansBuhid;
Feb 14 14:29:23 iMac Unknown[450]: },
Feb 14 14:29:23 iMac Unknown[450]: {
Feb 14 14:29:23 iMac Unknown[450]: UnicodeRange = "<__NSCFCharacterSet: 0x7fbc4acd0a80>";
Feb 14 14:29:23 iMac Unknown[450]: name = NotoSansHanunoo;
Feb 14 14:29:23 iMac Unknown[450]: },